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Ever wondered how your devices keep such precise timing? That’s thanks to the crystal oscillator. It uses a quartz crystal to create stable electrical signals. This technology powers everything from smartphones to satellites. With the global market for crystal oscillators projected to hit $4.2 billion by 2032, their importance keeps growing. What Are the Main Uses of Crystal Oscillators? Image Source: pexels Applications in Consumer Electronics Crystal oscillators are everywhere in your daily gadgets. They keep your clocks ticking, your radios tuned, and your computers running smoothly. Quartz-based products, in particular, have become the backbone of modern consumer electronics. Why? Because they offer unmatched precision and reliability. For instance, crystal oscillators are designed to handle temperature changes and aging without losing their accuracy. SiTime’s reliability tests even show a Mean Time Between Failures (MTBF) of 1140 million hours—30 times better than traditional quartz oscillators! This makes them perfect for critical devices like smartphones and laptops, where long-term performance matters. Role in Communication Systems Ever wondered how your phone call or internet connection stays clear and uninterrupted? That’s the magic of crystal oscillators. They ensure frequency stability, which is crucial for communication systems. Without it, you’d face issues like data corruption or dropped signals. Different types of oscillators, like temperature-compensated ones, adjust for environmental changes to maintain signal clarity. For example, RF communication oscillators generate precise carrier frequencies, ensuring your messages are transmitted and received without errors. This level of stability is what keeps modern communication systems running smoothly. Use in Industrial and Medical Devices Crystal oscillators also play a vital role in industries and healthcare. In medical devices, they ensure precise timing for diagnostic tools and monitoring systems. Imagine a heart monitor that’s even a second off—it could lead to incorrect readings. That’s why these oscillators are indispensable. They also shine in industrial applications, where high-precision timing is essential for automation and control systems. As technology advances, the demand for crystal oscillators in these fields continues to grow, proving their importance in critical applications. How to Choose the Right Crystal Oscillator Choosing the right crystal oscillator can feel overwhelming, but it doesn’t have to be. By focusing on a few key factors, you can find the perfect match for your circuit. Let’s break it down step by step. Key Factors to Consider When selecting a crystal oscillator, you’ll want to evaluate several important criteria. These factors ensure your oscillator delivers the performance and stability your application needs. Here’s what to keep in mind: Tip: Always check the datasheet for details like frequency tolerance and aging characteristics. These specs ensure your oscillator meets the required accuracy and stability. Understanding Frequency and Stability Frequency and stability are the heart of any crystal oscillator. But what do these terms really mean for your design? Let’s simplify it. Did you know? The Pierce crystal oscillator’s performance depends heavily on load capacitance. If the circuit’s capacitance doesn’t match the crystal’s specifications, the frequency can drift, causing instability. This highlights why understanding these parameters is so important. Matching the Oscillator to Your Circuit Now that you know the basics, it’s time to match the oscillator to your circuit. This step ensures your design works seamlessly. Pro Tip: If you’re designing for rugged environments, consider MEMS oscillators. They’re shock-resistant and reliable, though they may not match the precision of crystal oscillators. By following these steps, you’ll ensure your crystal oscillator delivers the high stability and performance your circuit needs. Common Issues with Crystal Oscillators Even the most reliable crystal oscillators can face challenges in real-world applications. Understanding these issues can help you troubleshoot problems and improve your circuit’s performance. Let’s dive into the most common ones and how to address them. Causes of Frequency Drift Frequency drift happens when the oscillator’s output frequency shifts over time or under changing conditions. This can disrupt your circuit’s stability and accuracy. But what causes it? Tip: Always check the datasheet for the oscillator’s temperature and aging specifications. This helps you pick a product that matches your application’s needs. Troubleshooting Startup Failures Startup failures occur when the oscillator doesn’t begin oscillating as expected. This can leave your circuit non-functional. Here’s what might be going wrong: Here’s a quick reference table to help you identify and fix common startup issues: Common IssueDescriptionSolutionFrequency ErrorActual frequency deviates from nominal frequencyChoose a product with the correct PPM value.Negative ImpedanceIncorrect negative impedance prevents oscillationAdjust external capacitors to meet impedance requirements.Excitation LevelsImproper excitation levels stop oscillationAdjust the excitation level in the circuit.Impurities on CrystalDust or residues hinder oscillationReplace the crystal and ensure clean manufacturing conditions. Note: Always follow the manufacturer’s guidelines for soldering and handling to avoid damaging the crystal during assembly. Resolving Noise and Interference Problems Noise and interference can degrade your oscillator’s performance, leading to unstable signals. Let’s break down the main culprits and how to tackle them: Pro Tip: Keep the oscillator away from high-frequency components in your circuit. This reduces the risk of interference and improves overall stability. By addressing these issues, you can ensure your crystal oscillator operates reliably and delivers the high stability your application demands. Advantages of Crystal Oscillators Image Source: pexels Superior Accuracy and Stability Crystal oscillators are unmatched when it comes to accuracy and stability. They maintain a steady frequency even under challenging conditions. This makes them ideal for applications where precision is critical, like communication systems or medical devices. Compared to alternatives like MEMS or ceramic oscillators, crystals perform significantly better. Here’s a quick comparison: MetricCrystal OscillatorsAlternative Sources (MEMS, Ceramic, SAW)Phase Noise Performance10-15 dB betterVariesTemperature Stability±10 ppm±50 ppm (MEMS), ±2500 ppm (Ceramic)Aging Rate<5 ppm/year10-20 ppm/year (MEMS), >20 ppm/year (Ceramic)Frequency Stability±10 ppmVariesQ Factor10,000-40,0001,000-2,000 (MEMS) This table shows why crystal oscillators are the go-to choice for high-performance applications. Their superior temperature stability and low aging rates ensure consistent performance over time. Long-Term Reliability When you need reliability, crystal oscillators deliver. They’re designed to maintain frequency stability within ±10–15 ppm over specific temperature ranges. This makes them perfect for mission-critical applications like remote sensing or medical monitoring. However, it’s important to note that quartz oscillators can be mechanically fragile. They may experience frequency drift under extreme conditions like shock or vibration. Despite this, their long-term reliability remains unmatched when used in controlled environments. By choosing oscillators with low aging rates (as little as ±3 ppm/year), you can minimize downtime and maintenance costs. Cost-Effectiveness for High-Performance Applications Crystal oscillators offer excellent value for high-performance circuits. While they might seem more expensive upfront, they save you money in the long run. For example, they reduce engineering time spent troubleshooting issues like startup failures or EMI compliance. Here’s a breakdown of potential savings: By addressing these issues early, you can avoid costly delays and ensure your circuits perform at their best. The high performance of an OCXO (oven-controlled crystal oscillator) further enhances cost-effectiveness by delivering unparalleled stability in demanding applications. Crystal oscillators are the backbone of precise timing in electronics. They’re everywhere—from your smartphone to industrial machines. By learning how to choose the right one and fix common issues, you can make your designs more reliable. Want proof of their importance? Check out these market insights: Report TitleKey FeaturesGlobal Active Crystal Oscillator Industry Research Report, Growth Trends and Competitive Analysis 2023-2029Tracks market dynamics and competition with verified data from 2018-2029.MEMS & Crystal Oscillators MarketHighlights the unmatched stability and precision of crystal oscillators. Their stability and reliability make them the go-to choice for countless applications. FAQ 1. Why is quartz crystal used in oscillators? Quartz crystal offers unmatched stability and precision for frequency control. Its piezoelectric properties make it ideal for maintaining consistent oscillations in various applications, from consumer electronics to communication systems. 2. What’s the difference between temperature-compensated and oven-controlled crystal oscillators? Temperature-compensated oscillators adjust for environmental changes, while oven-controlled crystal oscillators maintain a constant temperature for superior frequency control in demanding applications like aerospace or telecommunications. 3. How do I protect a quartz crystal from environmental damage? Seal the quartz crystal in a protective casing to shield it from humidity, dust, and vibration. This ensures long-term reliability and stable frequency control in your circuits.

 Overview of flicker noiseFlicker noise in oscillatorsFlicker Noise in SemiconductorFlicker Noise in op AmpHow to eliminate the flicker noise in op AmpThe working mechanism of flicker noiseEquation of flicker noiseThermal Noise vs. Flicker NoisePros of the flicker noiseCons of flicker noiseApplications of flicker noiseFlicker Noise FAQ Overview of flicker noiseElectronic noise known as flicker noise or 1/f noise happens naturally in almost all electronic parts. It can also result from contaminants in conductive channels, creation and recombination noise inside transistors due to base current, and other factors. Pink noise or 1/f noise are common names for this noise. All electrical devices commonly experience this noise, which has a variety of origins but is typically correlated with direct current flow. It is important in a variety of electronic fields and is important for oscillators used as RF sources.Because the power spectral density of this noise increases with frequency, it is sometimes referred to as low-frequency noise. Below a few KHz, this noise is generally visible. The flicker noise bandwidth ranges from 10 MHz to 10 Hz.Figure 1: The relationship between noise voltage and frequency Flicker noise in oscillatorsFlicker noise is inversely proportional to frequency, or 1/f, and in many applications, such as RF oscillators, there are parts where flicker noise, or 1/f noise, dominates, and other regions where white noise from sources like shot noise and thermal noise, or both, dominate. Within the oscillator the flicker noise expresses itself as sidebands that are near to the carrier, the other kinds of noise stretching away from the carrier with a smoother spectrum, however fading the larger the offset from the carrier.As a result, there is a corner frequency, fc, between the regions where the various types of noise predominate. It is typically discovered that the noise outside of the region where flicker noise predominates is phase noise for a system like an oscillator. As the offset from the carrier increases, this decays until flat white noise takes over.MOSFETs have a greater fc (which can reach GHz levels) than JFETs or bipolar transistors, whose fc is typically below 2 kHz. When building RF oscillators, flicker noise, or 1/f noise, is a crucial type of noise. Although it is frequently disregarded, its influence can be reduced by selecting the right gadget.Figure 2: Flicker noise in ocillators Flicker Noise in SemiconductorThe nature of semiconductor noise and how it is specified in semiconductor devices are covered in the section that follows. Since the origin of each semiconductor noise source is a random process, the noise's instantaneous amplitude is unpredictable. The distribution of the amplitude is Gaussian (normal).Figure 3: Flicker Noise in SemiconductorRemember that the RMS value of noise (Vn) equals the standard deviation (σ) of the noise distribution. A random noise source's RMS and peak voltages have the following relationship: VnP-P = 6.6 VnRMS. The crest factor of any signal is the ratio of peak-to-peak to RMS voltage (VnP-P/VnRMS). Because a Gaussian noise source statistically delivers peak-to-peak voltages that are 6.6 times the RMS voltage or higher 0.10% of the time, the crest factor in Equation 1 is 6.6. The likelihood of surpassing 3.3s is 0.001 in this shaded area under the noise voltage density curve in Figure 2. It's crucial to keep in mind that while random signals (like noise) multiply geometrically in a root sum square (RSS) way, associated signals add linearly. Flicker Noise in op AmpSince flicker noise occurs in addition to the thermal noise present in carbon composition resistors, it is frequently referred to as excess noise there. In varied degrees, other resistor types also show flicker noise, with wire coiled having the least. The type of resistor used will not impact the noise in the circuit because flicker noise is proportional to the DC current in the device, thus if the current is kept low enough, thermal noise will predominate. Scaling up resistors to minimize power consumption in an op amp circuit may result in a reduction in 1/f noise at the expense of an increase in thermal noise. Below is the formula to calculate the flicker noise:Figure 4: Flick noise formulaWhere Ke and Ki are proportionality constants (volts or amps) representing En and In at 1 Hz. fMAX and fMIN are the minimum and maximum frequencies in hertz. How to eliminate the flicker noise in op AmpWhat is the best way to deal with this loud, low-frequency noise? With the limited bandwidth, it is almost impossible to try and filter out this noise without changing the important signal. There is yet some hope, though. Although an amplifier's inherent 1/f noise is beyond the control of a system designer, this noise source can be reduced by choosing the right amplifier for the job. The best option is a zero-drift amplifier if 1/f noise is a major problem. Figure 5: zero-drift op amp chartAny amplifier that uses a constantly self-correcting architecture is referred to as "zero-drift" in the industry, regardless of whether it uses an auto-zero topology, a chopper-stabilized topology, or a combination of the two. No matter the specific architecture used, the objective of zero-drift amplifiers is to reduce offset and offset drift. Other dc features, such common-mode and power supply rejection, are also significantly enhanced during the procedure. The fact that the 1/f noise is eliminated during the offset correction procedure is another significant advantage of these self-correcting designs. This noise source occurs at the input and is relatively slow moving, hence it looks to be a component of the amplifiers offset and gets adjusted accordingly.  The working mechanism of flicker noiseBy raising the overall noise level above the thermal noise level, which exists in all resistors, flicker noise is produced. In contrast, wire-wound resistors have the least amount of flicker noise. This noise is merely present in thick-film and carbon-composition resistors, where it is referred to as surplus noise. Charge carriers that are sporadically trapped and released between the interfaces of two materials may be the source of this noise. Because instrumentation amplifiers use semiconductors to record electrical signals, this phenomena is common in those materials.This noise is merely inversely proportional to the frequency. There are various areas in many applications, such as RF oscillators, where noise predominates, and other areas where white noise from sources like shot noise & thermal noise predominates. A correctly constructed system is typically dominated by this low-frequency noise. Equation of flicker noiseSimply put, nearly all electronic components produce flicker noise. In light of this, the noise is discussed in respect to semiconductor devices, notably MOSFET devices. The formula for this noise is S(f) = K/f. Thermal Noise vs. Flicker NoiseThermal NoiseFlicker NoiseIn order to use SAR data both quantitatively and qualitatively, thermal noise must be eliminated by normalizing the backscatter signal throughout the whole SAR image.Several methods, like ac excitation and chopping, can be used to reduce this noise.The lower parasitic resistance components will result in a reduction in the intensity of thermal noise.Wherever the offset voltage of the amplifier is reduced, this noise intensity will be reduced using a chopper or chopper stabilization approach.Anytime current passes through a resistor, thermal noise results.Semiconductors used in instrumentation amplifiers to record various electrical signals typically experience this noise.Johnson noise, Nyquist noise, and Johnson-Nyquist noise are further names for this sound.1/f noise is another name for this noise.Thermal noise is the noise caused by the equilibrium thermal agitation of the electrons in an electrical conductor.Flicker noise is the sound produced by randomly trapped and released charge carriers at the interfaces of two materials. Pros of the flicker noiseAs the noise is low frequency, it will become quieter if the frequency increases.It is an innate noise present in semiconductor devices that is caused by their physics and manufacturing process.The effects are typically seen in electrical components at low frequencies. Cons of flicker noisePerformance can be hampered by this noise in any precision DC signal chain.In all varieties of resistors, the overall noise level can be raised above the thermal noise level.It is frequency dependant. Applications of flicker noiseCertain passive devices and all active electronic components contain this noise.This phenomena typically happens in semiconductors, which are primarily used to store electrical signals in instrumentation amplifiers.The amplifying capabilities of the device are limited by this noise in BJTs.In resistors made of carbon, this noise is present.This noise typically appears in active gadgets because the charge conveys unpredictable behavior. Flicker Noise FAQFlicker noise is measured in what ways?Similar to other types of noise measurement, flicker noise in current or voltage can be measured. The sampling spectrum analyzer instrument extracts a discrete sample from the noise and uses the FFT method to produce the Fourier transform. Low frequencies are beyond the capability of these sensors to accurately measure this noise. Thus, sampling equipment is wideband and has a high noise level. They can reduce the noise by averaging many sample traces. Due to its narrow-band acquisition, conventional-type spectrum analyzer equipment nonetheless have a higher SNR. What should I do to stop the flickering noise?By a chopper stabilization technique that lowers the amplifier's offset voltage, this noise can be effectively eliminated. Flicker Noise: Why Is It Pink?Pink noise, which has a spectral power density reduction of 3 dB per octave, is also known as flicker noise. As a result, the frequency has an inverse relationship with the pink noise band power. Lower power is produced at higher frequencies. Why is flickering called pink noise?One of the most frequently seen signals in biological systems is pink noise. The term originates from the pink appearance of visible light with this power range. White noise, on the other hand, has an equal strength throughout all frequency ranges. How is flicker noise measured?Flicker noise is proportional to the inverse of the frequency, i.e. 1/f and in many applications such as within RF oscillators there are sections in which the flicker noise, 1/f noise dominates and other regions where the white noise from sources such as shot noise and thermal noise dominate.

Introduction An oscillator is an electronic component used to generate an oscillating signal. The circuit composed of it is called an oscillating circuit, which can convert direct current into an electronic circuit or device with a certain frequency of alternating current signal. It is widely used in electronics industry, medical treatment, scientific research, etc. Catalog Introduction Ⅰ Oscillator Basics 1.1 Oscillator Meaning 1.2 Classification Rules Ⅱ Examples: RC Oscillator, LC Oscillator and Crystal Oscillator 2.1 RC Oscillator 2.2 LC Oscillator 2.3 Crystal Oscillator Ⅲ Selection Rules Ⅳ FAQ Ⅰ Oscillator Basics 1.1 Oscillator Meaning The oscillator is simply a frequency source and generally used in a phase-locked loop. In detail, it is a device that can convert DC power into AC power without external signal excitation. Generally divided into two types: positive feedback and negative resistance. The so-called oscillation, its meaning alludes to AC, and the oscillator includes a process and function starting from scratch. In other words, it can complete the conversion from DC power to AC power, such a device can be called an oscillator. 1.2 Classification Rules Oscillators are widely used, and there are many types:According to the oscillation frequency: high frequency oscillator, and low frequency oscillator.According to the oscillation waveform: sine wave oscillator, and non-sine wave oscillator.According to the oscillation feedback: positive feedback oscillator, and negative resistance oscillator.   Ⅱ Examples: RC Oscillator, LC Oscillator and Crystal Oscillator Electronic Oscillators || RC, LC, Crystal 2.1 RC Oscillator In a resistance-capacitance oscillator or short for RC oscillator, by using RC components in the feedback branch, a phase shift occurs between the input of the RC network and the output from the same network. The input is again moved through the second inverting stage, giving a phase shift, which is the same as providing the required positive feedback. It is suitable for low frequency oscillation, and is generally used to generate low frequency signals of 1Hz to 1MHz. The circuit is composed of four parts: amplifying circuit, frequency selection network, positive feedback network, and amplitude stabilization. The main advantages of it are simple structure, economic and convenient, and belong to the audio frequency oscillator. Figure 1. RC Oscillator Circuit (1) Vibration ProcessWhen the power is just turned on, there are various electrical disturbances in the circuit, and a relatively large feedback voltage is generated through feedback through the frequency selection network. Passing through the continuous loop of linear amplification and feedback, the oscillation voltage will continue to increase.(2) Oscillation FrequencyThe oscillation frequency is determined by the phase balance condition., Only meets the phase balance condition at f0, the oscillation frequency is .Changing R and C can change the oscillation frequency.(3) Conditions for Start-up and Stable OscillationTaking into account the starting conditions of AuF>1, generally Rt should be selected slightly larger than 2R1. If this value is too large, it will cause serious distortion of the oscillation waveform.The RC series-parallel sine-wave oscillator circuit composed of an op amp does not rely on the transistor inside the op amp to enter the nonlinear region to stabilize the amplitude, but to achieve the purpose of amplitude stabilization by introducing negative feedback from the outside.(4) Stable AmplitudeThe growth process of the oscillation amplitude cannot continue forever, when the amplifier gradually enters the saturation or cut-off zone from the amplification zone. Working in a non-linear state, its gain gradually decreases. When the amplifier gain decreases and the loop gain decreases to 1, the amplitude increase process will stop and the oscillator will reach equilibrium.For the RC oscillator circuit, increasing the resistance can reduce the oscillation frequency, and it does not need to increase the cost. The frequency of the sine wave generated by the commonly used LC oscillation circuit is relatively high. If a low frequency sine oscillation is to be generated, the oscillation circuit must have a larger inductance and capacitance. This will not only cause the components to be bulky, heavy, and inconvenient to install, but also difficult to manufacture with high cost. Therefore, the sinusoidal oscillation circuit below 200kHz generally adopts an RC oscillation circuit with a lower oscillation frequency.   2.2 LC Oscillator LC oscillator is also called LC oscillating circuit, resonance circuit, tank circuit or tuning circuit. It consists of a capacitor and a parallel coil. The circuit has an inductor L and a capacitor C. Capacitors store energy in the form of electrostatic fields and generate potential on their plates, while inductance coils store energy in the form of electromagnetic fields. By placing the switch in a specific position, the capacitor is charged to the DC supply voltage. When the capacitor is fully charged, the switch is switched to a certain position, and the charged capacitor is connected in parallel to the inductor coil, so the capacitor starts to discharge itself through the coil. Figure 2. LC Oscillator Circuit The LC circuit is not only used to generate a specific frequency signal, but also used to separate a specific frequency signal from a more complex signal. They are key components in many electronic equipment, especially radio equipment, used in oscillators, filters, tuners and mixer circuits.The inductive circuit is an idealized model because it assumes that there is no energy dissipated due to resistance. The actual realization of any LC circuit will include the loss caused by the small but non-zero resistance of the components and connecting wires. The purpose of an LC circuit is usually to minimize oscillations, so the resistance is made as small as possible. Although there is no lossless circuit in practice, studying the ideal form of this circuit is beneficial to study physical phenomenon.When electromagnetic oscillation occurs in an oscillating circuit, if there is no energy loss and no external influences, the period and frequency of it at this time are called the natural frequency and natural period of the oscillating circuit. The natural period can be obtained by the following formula: Where, the time constant is L/R. What are LC Oscillations? 2.3 Crystal Oscillator Some electronic devices require an AC signal with a highly stable frequency, but the LC oscillator has poor stability and the frequency is easy to drift (that is, the frequency of the generated AC signal is easy to change). A special component-quartz crystal is used in the oscillator, which can generate a highly stable signal. This kind of oscillator that uses a quartz crystal is called a crystal oscillator. It is mainly composed of a crystal and peripheral components. In a crystal oscillator, the main frequency determining element is a quartz crystal. Due to the inherent characteristics of the quartz crystal oscillator, it has extremely high frequency stability. Temperature compensation may be related to the crystal oscillator to improve the thermal stability. Because it is a fixed frequency oscillator, stability and accuracy are the basic considerations when use it. Figure 3. Crystal Oscillator Circuit The crystal oscillator has a piezoelectric effect, that is, the crystal will deform when a voltage is applied to the two poles of the wafer. Conversely, if an external force deforms the wafer, the metal sheets on the two poles will generate voltage. If an appropriate alternating voltage is applied to the chip, the chip will resonate (the resonance frequency is related to the tilt angle of the quartz slope, etc., and the frequency is constant). The crystal oscillator uses a crystal that can convert electrical energy and mechanical energy into each other. It can provide stable and accurate single-frequency oscillation when working in a resonance state. Under normal working conditions, the absolute accuracy of ordinary crystal oscillator frequencies can reach 50 parts per million. Using this feature, the crystal oscillator can provide a more stable pulse, which is widely used in the clock circuit of the microchip. In addition, the wafers are mostly quartz semiconductor materials, and the shell is encapsulated with metal.The main parameters of the crystal oscillator include nominal frequency, load capacitance, frequency accuracy, frequency stability, etc. These parameters determine the quality and performance of the crystal oscillator. Therefore, in practical applications, an appropriate crystal oscillator should be selected according to specific requirements. For example, systems such as communication networks and wireless data transmission require high-precision crystal oscillators. However, since the higher the performance of the crystal oscillator is, the more expensive it is, so you can choose a crystal that meets the requirements when buying.   Ⅲ Selection Rules Oscillators are used in many electronic products. In order to ensure the normal operation of electronic products, the selection of oscillators is important. The following summarizes the five selection rules for reference.1) Appearance InspectionBy checking the appearance of the product, whether the marking text is clear and standard, whether there are cracks on the surface of the appearance, and whether the pins have been soldered. If the product is found to be imperfect on the outside, it should not be used.2) FrequencyChoose the appropriate frequency according to the actual product requirements. The frequency is the most important, and it cannot be replaced casually. Negotiations must be conducted after passing the qualification verification or professional test. If the frequency required by the actual circuit is 5MHZ, do not replace it with a similar frequency without any original replacement.3) Output ModeWhen choosing a oscillator, consider the type of oscillator output required by the circuit, which generally divided into level output and differential output. As for level output, CMOS is the most commonly used type, and in terms of differential output, LVPECL(Low Voltage Positive Emitter-Couple Logic) and LVDS (Low-Voltage Differential Signaling) are commonly used differential output type. Different output types cannot be changed randomly, especially differential and ordinary oscillators.4) ModelTo use the oscillator, you must see the model mark of the shell. The model number indicates its multiple parameters. According to the product requirements, the corresponding product parameters can be found, and the same model can be found later. If the crystal oscillator model is not selected properly, it will cause errors in the application.5) ReplacementIf an oscillator is damaged, it should be replaced by the original model in principle. When the original model is not available, it is best to consider replacing it with another model or other type of oscillator after testing.   Ⅳ FAQ 1. What is oscillator and its types?An oscillator is a type of circuit that controls the repetitive discharge of a signal, and there are two main types of oscillator; a relaxation, or an harmonic oscillator. This signal is often used in devices that require a measured, continual motion that can be used for some other purpose. 2. What are the types of oscillator in electronics?There are two main types of electronic oscillator – the linear or harmonic oscillator and the nonlinear or relaxation oscillator. 3. How many types of oscillations are there?There are 3 main types of Oscillation – Free, damped, and forced oscillation. When a body vibrates with its own frequency, it is called a free oscillation. 4. What is RC and LC oscillator?The oscillation frequency is proportional to the inverse of the capacitance or resistance, whereas in an LC oscillator the frequency is proportional to inverse square root of the capacitance or inductance. So a much wider frequency range can be covered by a given variable capacitor in an RC oscillator. 5. What is the principle of oscillator?There are many types of electronic oscillators, but they all operate according to the same basic principle: an oscillator always employs a sensitive amplifier whose output is fed back to the input in phase. Thus, the signal regenerates and sustains itself. This is known as positive feedback. 6. What are the three types of oscillator?The main types of Oscillators include: Wien Bridge Oscillator. RC Phase Shift Oscillator. Hartley Oscillator. 7. What is the use of LC oscillator?LC oscillators are used in heating with high-frequency, RF generators, radios, TV receivers, etc. These types of oscillators use tank circuits including the components like a capacitor (C) and an inductor (L). 8. What does RC oscillator do?RC oscillators are a type of feedback oscillator; they consist of an amplifying device, a transistor, vacuum tube, or op-amp, with some of its output energy fed back into its input through a network of resistors and capacitors, an RC network, to achieve positive feedback, causing it to generate an oscillating. 9. What is RC phase oscillator?RC phase-shift oscillators use resistor-capacitor (RC) network to provide the phase-shift required by the feedback signal. They have excellent frequency stability and can yield a pure sine wave for a wide range of loads. ... Further, the circuit also shows three RC networks employed in the feedback path. 10. What are the advantages of RC oscillator?The RC phase shift oscillator gives good Frequency stability. The output of this circuit is sinusoidal that is quite distortion free.. It is suitable for lower frequencies and this lower limit exists in as low as 1Hz. RC phase shift oscillators don't require any negative feedback and stabilization arrangements. 11. What is a crystal oscillator used for?A crystal oscillator is an electronic oscillator circuit that is used for the mechanical resonance of a vibrating crystal of piezoelectric material. It will create an electrical signal with a given frequency. 12. What are the advantages of crystal oscillator?The Advantages of a Crystal OscillatorStability. Stability is one of the most important requirements of any oscillator.High Q. The Q factor or quality factor describes how 'underdamped' oscillators are.Frequency Customization and Range.Low Phase Noise.A Crystal Oscillator Is Compact and Inexpensive. 13. What is crystal oscillator explain?A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a constant frequency. ... Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz.

Ⅰ IntroductionOscillators are the heartbeat of modern electronics. From the quartz watch on your wrist to the 5G smartphone in your pocket, these components play a critical role in generating timekeeping signals and carrier waves. While early applications included simple AM radios and metal detectors, today's oscillators are foundational to IoT devices, advanced computing, and high-speed data transmission.To understand how electronic oscillators function in 2025, it helps to look at physical analogies and fundamental circuit designs. This guide covers the core concepts, modern classifications, and practical examples of oscillators in electronics.Ⅱ What is an Oscillator?An oscillator is an electronic circuit that converts direct current (DC) from a power supply into an alternating current (AC) signal—typically a sine wave, square wave, or triangle wave. They are ubiquitous in technology, found in everything from microcontrollers and music synthesizers to GPS receivers.Every oscillator contains at least one active device (such as a transistor or Op-Amp) that acts as an amplifier. The core operating principle relies on a feedback loop: an oscillator employs a sensitive amplifier where a portion of the output signal is fed back into the input in phase. This process, known as positive feedback, allows the signal to regenerate and sustain itself indefinitely, provided there is a power source.Ⅲ The Working Principle of an OscillatorFor an oscillator to sustain a frequency, energy must oscillate between two forms. The simplest way to visualize this is through a Tank Circuit, created by connecting a capacitor and an inductor in parallel.The Energy Cycle:Storage: Capacitors store energy in an electrostatic field, while inductors store energy in a magnetic field.Discharge: When a charged capacitor discharges through an inductor, the current creates a magnetic field around the inductor coil.Collapse & Recharge: As the capacitor fully discharges, the inductor's magnetic field collapses, inducing a current that recharges the capacitor (with opposite polarity).Oscillation: This back-and-forth transfer of energy creates an oscillation. In a perfect world, this would continue forever. In reality, internal resistance dissipates energy (damping), so an active component (amplifier) is required to inject energy and keep the oscillation going.Ⅳ Types of Oscillators4.1 General ClassificationWhile there are countless variations, oscillators generally fall into two primary categories:Harmonic (Linear) Oscillators: Energy flows from active to passive components to generate a purely sinusoidal waveform. The frequency is determined by a feedback path. These are crucial for radio frequencies (RF) and audio applications.Relaxation Oscillators: These operate by exchanging energy between active and passive components through charging and discharging phases. They produce non-sinusoidal shapes like square, saw-tooth, or triangular waves, commonly used in digital timing and signal processing.4.2 The 5 Basic TypesRC and LC Oscillators: Basic circuits using resistors/capacitors or inductors/capacitors to determine frequency.Crystal Oscillators: Use vibrating quartz crystals (and increasingly MEMS technology) for high-precision stability.Sinewave Oscillators: Circuits optimized to produce low-distortion sine outputs (e.g., Wien Bridge).Square Wave Oscillators: Circuits like the Multivibrator or 555 Timer used for clock pulses.Voltage Controlled Oscillators (VCO): The frequency output can be tuned by varying the input voltage.Ⅴ Details and Circuit Examples5.1 LC OscillatorsLC oscillators combine inductors and capacitors (a tank circuit) to generate high-frequency sine waves. They are preferred in Radio Frequency (RF) applications because they offer good phase noise performance and are easy to tune. In 2025, advanced LC tank circuits are still relevant in communication hardware, though they are often integrated into silicon chips.Figure 1: Basic LC Oscillator ConfigurationExample: Gated LC Phase Shift OscillatorThis circuit allows the oscillation to be turned on or off via a logic input. When the input is high (e.g., 5V), the oscillator runs; when grounded, it stops. This "burst" mode capability is useful in digital communication protocols.Figure 2: Gated LC Phase Shift Oscillator5.2 RC (or CR) OscillatorsAt low frequencies (like the audio range of 20Hz - 20kHz), inductors become large and impractical. Engineers solve this by using Resistors and Capacitors (RC) to set the frequency. While creating a pure sine wave with RC circuits is challenging, they are cost-effective and compact for audio signal generation.Figure 3: Basic RC OscillatorExample: CMOS 555 Timer & Schmitt TriggerEven decades after its invention, the 555 timer remains a staple in electronics. The modern CMOS versions consume less power and offer cleaner switching, making them ideal for battery-operated IoT sensor polling.Figure 4: 555 Timer based RC Oscillator5.3 Crystal OscillatorsCrystal oscillators utilize the piezoelectric effect of quartz to generate a frequency with immense stability. They act as the "heartbeat" for microprocessors. In recent years, MEMS (Micro-Electro-Mechanical Systems) oscillators have begun to replace quartz in some high-vibration environments, but quartz remains the standard for precision.Figure 5: Crystal Oscillator SchematicFor High-Frequency (HF) applications, a transistor like the 2N2222A (or modern surface-mount equivalents) is typically used. The tuned circuit matches the impedance, often loading at nominally 50 ohms. Modern designs frequently include a buffer amplifier stage to prevent the load from pulling the crystal off-frequency.5.4 Sinewave OscillatorsThe Wien Bridge Oscillator is a specific type of RC oscillator capable of generating very low-distortion sine waves. It is famous for being the first product designed by Hewlett-Packard (HP).Figure 6: Practical Wien Bridge Oscillator using a light bulb for stabilizationHistorical Note: The schematic above uses an incandescent light bulb for gain stabilization. As the bulb heats up, its resistance increases, stabilizing the feedback loop. In modern 2025 circuitry, this bulb is typically replaced by JFETs or automatic gain control (AGC) ICs for higher reliability and lower power consumption, though the bulb method remains an excellent educational example of negative feedback.5.5 Square Wave OscillatorsAlso known as Astable Multivibrators, these generate a digital on/off signal without external input. They are fundamental to digital logic clocks and PWM (Pulse Width Modulation) controllers.Figure 7: Multi-frequency Square Wave Generator using 555 Timer5.6 Voltage Controlled Oscillator (VCO)A VCO allows the frequency to be tuned dynamically by changing a control voltage. This is the core component of Phase Locked Loops (PLLs) used in Wi-Fi, Bluetooth, and cellular radios to lock onto specific frequencies.In the circuit below, a Varactor Diode is used. When reverse-biased, a diode acts like a capacitor; varying the voltage changes the capacitance, thus tuning the oscillator circuit without moving parts.Figure 8: Hartley Oscillator configuration for VCO applicationsⅥ Frequently Asked Questions (FAQ)1. What is the primary function of an oscillator?Oscillators convert a steady DC supply into a periodic AC signal. They provide the timing signals (clock) for computers, generate carrier waves for wireless transmission, and produce audio signals for synthesizers and alarms.2. How do you calculate oscillation frequency?For a simple pendulum or mechanical system, the formula is T = 2π√(m/k). In electronics (LC circuit), the resonant frequency is calculated as f = 1 / (2π√(LC)), where L is inductance and C is capacitance.3. What are the core components of an oscillator circuit?Most oscillators require three elements: 1. Tank Circuit/Network: Passive components (Inductors/Capacitors or Crystals) to set the frequency. 2. Amplifier: An active device (Transistor, Op-Amp) to gain power. 3. Feedback Loop: A positive feedback path to sustain the oscillation.4. What is the difference between an oscillator and an alternator?While both generate AC, an alternator is a mechanical device that converts mechanical energy into electrical energy (usually at low frequencies like 50/60Hz). An electronic oscillator is a solid-state circuit that converts DC electrical energy into high-frequency AC signals without moving parts.

IntroductionSimply put, an oscillator is a device that can convert DC power into AC power without external signal excitation. The so-called "oscillation" implies alternating current. This article will mainly explain the circuits of different sine wave oscillators, including their working principles, how to realize their functions, circuit composition and comparison of advantages and disadvantages of different forms of circuits. This article uses a large number of circuit diagrams and formulas to explain in detail, which can help you understand in a better way.Basics of oscillators and their different typesCatalogIntroductionCatalogI The Principle of Feedback Oscillator1.1 How Does the Feedback Oscillator Work?1.2 Equilibrium Conditions1.3 Starting Conditions of the Oscillator1.4 Stable Conditions of the Oscillator1.5 General Composition of Sine Wave OscillatorII LC Oscillator Circuit2.1 The Composition Principle of the Oscillator2.2 Capacitive Feedback Oscillator2.3 Inductive feedback oscillatorIII RC Oscillator Circuit3.1 Brief Introduction of RC Oscillator and its Circuit3.2 RC Phase Shift Oscillator3.3 Wien Bridge OscillatorIV Quartz Crystal Oscillator Circuit4.1 What is a Quartz Crystal Oscillator?4.2 Quartz Crystal4.3 Quartz Crystal Oscillator CircuitV Non-sine Wave Generating Circuit5.1 What is a Non-sine Wave Generating Circuit?5.2 Rectangular Wave Generator5.3 Triangle Wave and Sawtooth Wave Signal GeneratorVI QuizⅦ FAQI The Principle of Feedback Oscillator1.1 How Does the Feedback Oscillator Work?The feedback oscillator is when the power is turned on, the various electrical disturbance signals in the loop are selected by the frequency selection network, and the signal of a certain frequency is fed back to the input terminal, and then the cycle of amplification → feedback → amplification → feedback , The amplitude of the signal increases continuously, and the oscillation is established from small to large. As the signal amplitude increases, the amplifier will enter a non-linear state, and the gain will decrease. When the feedback voltage is exactly equal to the input voltage, the oscillation amplitude will no longer increase and enter a balanced state. As can be seen from the figure below, the feedback oscillator is a closed loop composed of an amplifier and a feedback network. The amplifier is usually a tuned amplifier with an oscillation circuit as a load. The feedback network is generally a linear network composed of passive components.Figure1. Block Diagram of Feedback OscillatorIn order to generate self-oscillation, there must be positive feedback, that is, the signal fed back to the input terminal and the signal at the input terminal of the amplifier have the same phase. For the above figure, suppose the voltage amplification factor of the amplifier is K(s), the voltage feedback coefficient of the feedback network is F(s), and the closed-loop voltage amplification factor is Ku(s), thenby We can writeIf a certain frequency ω1=ω, then T(jω1) is equal to 1. From the above formula, we can see that Ku(jω) will tend to infinity. This shows that there is no external signal, and self-excited to produce signal output, namely self-oscillation. Therefore, the condition of self-oscillation is that the loop gain is 1.Definition:1.2 Equilibrium ConditionsThe equilibrium condition of the oscillator isthis can also be expressed asIf a certain frequency ω1=ω, then T(jω1) is equal to 1. From the above formula, we can see that Ku(jω) will tend to infinity. This shows that there is no external signal, and self-excited to produce signal output, namely self-oscillation. Therefore, the condition of self-oscillation is that the loop gain is 1. The above two formulas are the amplitude and the phase equilibrium conditions respectively. Equilibrium conditions are also called "two conditions for maintaining self-oscillation". The amplitude balance condition determines the amplitude of the oscillator output signal, and the phase equilibrium condition determines the frequency of the oscillator output signal. But it must be pointed out that the loop can only meet the phase equilibrium condition at a certain frequency (f), which is the resonant frequency (f0) of the loop.1.3 Starting Conditions of the OscillatorWhen the oscillator is in actual application, there should be no external signal Us(s) shown in Figure 1. The initial source of oscillation is electrical signals such as electrical shock and various thermal noises that inevitably exist when the oscillator is switched on.It can be seen from the establishment process of the oscillation that in order to make the oscillator start-up, the feedback voltage Uf and the input voltage Ui should be in phase at the beginning of the oscillation (that is, positive feedback); Uf>Ui should be required in amplitude, that is:Vibration conditions: φA+φF=2nπ(n=0,1,2,•••)AF>1 Simply put, as we know, the condition of unity gain must be met to make the oscillation continue. But to start the oscillation, the voltage gain of the positive feedback loop must be greater than 1, so that the amplitude of the output voltage can reach the required potential. Then the gain must be reduced to 1, so that the output voltage can be maintained at the required potential and the oscillation phenomenon can continue. Transition from |T(jω)|>1 to |T(jω)|=1 when the oscillator is workingThe amplifier must work in the linear amplification region of the transistor when amplifying small signals.When the oscillation is started, the amplifier works in the linear region. At this time, the output of the amplifier increases linearly with the increase of the input signal; as the amplitude of the input signal increases, the amplifier gradually enters the saturation or cut-off region from the amplification region, and enters a nonlinear state. The closed-loop gain of will decrease with the increase of the input signal, as shown in the figure below:Figure2. Graphical Representation of Amplitude ConditionsWhen the loop gain drops to |T(jω)|=1, the growth process of the amplitude will stop, and the oscillator will reach a balanced state and perform constant amplitude oscillation. It can be seen that the transition of the oscillator from amplified oscillation to steady amplitude oscillation is realized by the non-linear characteristics of the amplifier. When the oscillating circuit is powered on, the current of the transistor increases abruptly from zero, and the sudden change current contains a wide spectrum component. The start-up process of the circuit is very short! As long as the circuit satisfies the starting conditions, after the oscillator is powered on, there will be an output signal with stable amplitude at the output.Figure3. Circuit Start-up Process1.4 Stable Conditions of the OscillatorIf the loop gain characteristic has two equilibrium points A and B, among them, point A is stable and point B is unstable.Figure4. Stable Conditions of the OscillatorIt can be seen from the above discussion that in order to stabilize the equilibrium point, |T(ω0)| must have a negative slope change near UiA.Stable conditions are divided into amplitude stable conditions and phase stable conditionsTo make the amplitude stable, the oscillator must have the ability to prevent amplitude changes at its equilibrium point. Then the amplitude stability condition should beSince the feedback network is a linear network, which means the size of the feedback coefficient does not change with the input signal, so the amplitude stability condition can be written asThe phase stability depends on the increase of ω, and the decrease of , meaning that the phase characteristic of the parallel oscillator circuit ensures the phase stability.Therefore, the phase stability condition is. The higher the Q value of the loop,  the larger of the value of , and the better phase stability.1.5 General Composition of Sine Wave Oscillator(1) Amplifying circuit-realize energy control.(2) Positive feedback network-meets the conditions for starting vibration.(3) Frequency selection network-only one frequency satisfies the oscillation condition to obtain a sine wave output of a single frequency. Commonly used frequency selection networks include RC frequency selection and LC frequency selection(4) Amplitude stabilization link-makes the circuit easy to start and oscillate stably, with little waveform distortion. Examples of oscillation circuits:High frequency resonant amplifier and sine wave oscillatorFigure5. High Frequency Small Signal Resonant AmplifierFigure6. Mutual Inductance Coupled OscillatorII LC Oscillator CircuitLC oscillators can be divided into three types: mutual inductance coupled oscillators, inductive feedback oscillators and capacitive feedback oscillators according to their different feedback networks.This section focuses on different types of feedback LC oscillators and three-point oscillators.2.1 The Composition Principle of the OscillatorFigure7. General Form of Three-terminal OscillatorThe basic circuit is the so-called three-terminal (also called three-point) oscillator, which means the circuit formed by connecting the three terminals of the LC loop and the three electrodes of the transistor respectively, as shown in the figure. The three-terminal LC oscillator is a feedback type LC oscillator. In order to obtain positive feedback, the feedback circuit must make the instantaneous polarity of the transistor's AC voltage meet a certain phase relationship: when Vbe is negative, Vce should be positive, namely, Vbe and Vce are in reverse phase, and Veb and Vce are in phase. Only when the reactance Xce and Xeb have the same properties can they be guaranteed to be in phase. When the resistance of the loop element is very small, its influence can be ignored, and the influence of the input impedance and output impedance of the transistor can also be ignored. To maintain oscillation, the circuit must meet the requirements. Otherwise, the loop resonance condition cannot be met.The criteria for the three-terminal oscillator circuit to meet the phase equilibrium condition is as follows:(1) The reactance properties of Xce and Xeb are the same, but the reactance properties of Xcb are opposite. That is, ce and be are the same resisting piece, and cb resisting piece.(2) The oscillation frequency should satisfy 1Xo+Xcl-XolBased on this criterion, it can be quickly judged whether the oscillating circuit composition is reasonable or not.Three-terminal LC oscillatorThe three-terminal LC oscillation circuit is often used, and its operating frequency is about a few MHz to a few hundred MHz. The frequency stability is also higher than that of the transformer coupled oscillation circuit, which is about 10-3~10-4. After some frequency stabilization measures, it can be higher. There are many types of three-terminal LC oscillators, mainly: Inductance three-terminal type, also known as Hartley oscillator; capacitor three-terminal type, also known as Colpitts oscillator; series type improved capacitor three-terminal type, also known as Clapp parallel type improved capacitor three-terminal type , Also known as Sellier oscillator. The three-terminal oscillator has two basic circuits, as shown in the figure below.Figure8. Capacitive Feedback Oscillator and Inductive Feedback Oscillator2.2 Capacitive Feedback OscillatorCapacitive feedback three-terminal oscillator is an electronic component, also called Colpitts oscillator, which is a kind of self-excited oscillator. It is composed of a series capacitor, an inductance circuit and a positive feedback amplifier. It is named because the three end points of the two series capacitors of the oscillating circuit are connected to the three pins of the oscillating tube respectively.Figure9. Capacitive Feedback OscillatorAs shown in the figure, use C2 to feed back part of the voltage of the resonant tank to the base. The three end points of the LC resonant tank are respectively connected to the three electrodes of the transistor, so it is called a capacitive feedback three-terminal oscillator, or Colpitts oscillator. The vector analysis method can be used to prove that the circuit meets the phase balance condition. As long as the ratio of C1 and C2 is appropriately selected and the amplifier has enough amplification, the circuit can oscillate.Figure10. Capacitive Feedback OscillatorAdvantages of Colpitts circuit:(1) Good oscillation waveform;(2) The frequency stability of the circuit is high. If the capacitance of the circuit is increased appropriately, the influence of unstable factors on the oscillation frequency can be reduced;(3) The operating frequency of the three-terminal circuit of the capacitor can be made higher. The output and input capacitors of the oscillator tube can be directly used as the oscillation capacitor of the loop, and the operating frequency can reach a very high frequency range of tens of MHz to hundreds of МHz. Disadvantages of Colpitts circuit:When adjusting C1 and C2 to change the oscillation frequency, the feedback coefficient will also change, which will affect the starting conditions and working status. But as long as a variable capacitor is connected to both ends of L and C1 and C2 are fixed capacitors, the feedback coefficient will not be affected when the frequency is adjusted.2.3 Inductive feedback oscillator(1) Circuit compositionIn order to overcome the shortcomings that the transformer primary coil and the secondary coil in the transformer feedback oscillation circuit are not tightly coupled, the N1 and N2 of the transformer feedback oscillation circuit can be combined into one coil. As shown in the figure below, in order to strengthen the resonance effect, the capacitor C is connected across the entire coil. This is the inductive feedback oscillator circuit, or Harley oscillator.Figure11. Inductive Feedback Oscillator Circuit(2) Working principle✿The circuit includes four parts: amplifier circuit, frequency selection network, feedback network and non-linear element (transistor), and the amplifier circuit can work normally.✿Use the instantaneous polarity method to judge whether the circuit meets the phase condition of sine wave oscillation: disconnect the feedback, add the input voltage with frequency f0, give its polarity, and judge that the polarity of the feedback voltage obtained from N2 is the same as the input voltage , So the circuit satisfies the phase condition of sine wave oscillation.✿As long as the circuit parameters are selected properly, the circuit can meet the amplitude condition and produce sine wave oscillation. The following figure shows the AC path of the inductive feedback oscillation circuit. The three ends of the primary coil are connected to the three poles of the transistor, so the inductive feedback oscillation circuit is called an inductive three-point circuit.Figure12. AC Path of Inductive Feedback Oscillator Circuit(3) Advantages and disadvantagesThe coupling between N2 and N1 in the inductance feedback oscillation circuit is tight, the amplitude is large, and it is easy to oscillate; when C uses a variable capacitor, a wide adjustment range of oscillation frequency can be obtained, and the highest oscillation frequency can reach tens of MHz. Since the feedback voltage is taken from inductance, it has greater reactance to high-frequency signals, and the feedback signal contains more high-order harmonic components, and the output voltage waveform is not good. The following introduces two improved capacitor three-terminal oscillation circuits:Clap oscillator:The following figure (a) is the principle circuit of the Krapper oscillator, and (b) is its AC equivalent circuit. Its characteristic is that a capacitor C3 is added to the inductance branch of the aforementioned capacitive three-point oscillating resonant tank. Its value is relatively small, requiring C3<< C1, C3<< C2.Figure13. Clapp OscillatorRegardless of the influence of the capacitance between the poles, the total capacitance CΣ of the resonant circuit is the series connection of C1, C2 and C3, namely. Thus, the oscillation frequency is .The condition for the above formula to be true is that C1 and C2 must be selected relatively large. It can be seen that the influence of C1 and C2 on the oscillation frequency is significantly reduced, so the influence of the capacitance between the transistors connected in parallel with C1 and C2 is also very large. It is smaller, and the stability of the oscillation frequency is improved. Sellier oscillator:Figure14. Sellier Oscillator so the oscillation frequency:L is the inductance of the inductance coil of the resonant amplifier circuit; C is the total capacitance of the resonant circuit. In the LC resonance circuit, the inductance L(H)/capacitance C(F)=105~106, which can achieve better results.III RC Oscillator Circuit3.1 Brief Introduction of RC Oscillator and its Circuit● What is an RC oscillator?(1) The sine wave oscillator has no input signal and is a positive feedback amplifier with a frequency selection network. If resistors and capacitors are used to form a frequency selection network, it is called an RC oscillator, which is generally used to generate 1Hz-1MHz low-frequency signals. The frequency selection effect of the RC frequency selection network is not as good as that of the LC resonant circuit, so the waveform and stability of the RC oscillator are worse than that of the LC oscillator.(2) RC oscillator can be divided into sine wave oscillator and non-sine wave oscillator according to whether the output wave type is sine wave.(3) There are many kinds of RC oscillation circuits: bridge type, phase shift type, double T type, the most commonly used is bridge type oscillation circuit, namely RC series-parallel frequency selection network. ● Features of RC oscillator(1) RC phase-shift oscillator features: simple, poor frequency selection, unstable amplitude, inconvenient frequency adjustment, generally used in occasions with fixed frequency and low stability requirements. Frequency range: several hertz-tens of kilohertz(2) RC series-parallel network oscillator features: it can easily and continuously change the oscillation frequency, it is convenient to add negative feedback to stabilize the amplitude, and it is easy to get a good oscillation waveform.(3) Double T frequency selective network oscillator characteristics: good frequency selection characteristics, difficult frequency modulation, suitable for generating single frequency oscillation. ● RC oscillator circuitThe oscillating circuit composed of RC frequency selection network is called RC oscillating circuit, which is suitable for low-frequency oscillation, and is generally used to generate low-frequency signals of 1Hz~1MHz. The circuit is composed of four parts: amplifier circuit, frequency selection network, positive feedback network, and amplitude stabilization link. The main advantage is simple structure, economic and convenient. According to the different forms of the RC frequency selection network, the RC oscillator circuit can be divided into an RC lead (or lag) phase shift oscillator circuit and a Wien circuit oscillator circuit. For RC oscillator circuits, increasing the resistance R can reduce the oscillation frequency, and increasing the resistance does not need to increase the cost. The frequency of the sine wave generated by the commonly used LC oscillator circuit is relatively high. If a sine wave with a lower frequency is to be generated, the oscillation circuit must have a larger inductance and capacitance. This will not only cause the components to be bulky, heavy and inconvenient to install, but also difficult to manufacture. high cost.  Therefore, the sinusoidal oscillation circuit below 200kHz generally adopts an RC oscillation circuit with a lower oscillation frequency.3.2 RC Phase Shift OscillatorThe phase shift oscillator is an oscillator composed of an advanced phase shift or a lag phase shift circuit as a frequency selection network and an inverting amplifier. It has the advantages of simple circuit, economy and convenience, but the effect of frequency selection is poor, the amplitude is not stable enough, and the frequency adjustment is inconvenient. Therefore, it is generally used for occasions with fixed frequency and low stability requirements. Its oscillation frequency is:Figure15. RC Phase Shift Oscillator Schematic Diagram3.3 Wien Bridge OscillatorThe RC series-parallel frequency selection network and amplifier can be combined to form an RC oscillator circuit, and the amplifier part can be an integrated operational amplifier. As shown in the figure, the RC series-parallel frequency selection network is connected between the output of the operational amplifier and the non-inverting input to form positive feedback. Rt and R1 are connected between the output of the operational amplifier and the inverting input to form negative feedback. . The positive feedback circuit and the negative feedback circuit constitute a Wien bridge circuit, and the input and output ends of the operational amplifier are respectively connected across the diagonal of the bridge. Therefore, this kind of oscillation circuit is called a Wien bridge oscillation circuit.Figure16. Wien Bridge OscillatorThe oscillating signal is input from the non-inverting terminal, so a non-inverting amplifier is formed. The output voltage is in phase with the input voltage, and the closed-loop voltage amplification factor is equal to: When the RC series-parallel frequency selection network is ω=ω0=1/RC, Fu=1/3, εf=0, so as long as |Au|=1+(Rt/R1)>3, that is, Rt>2R1, oscillation The circuit can meet the self-excited oscillation amplitude and phase start-up conditions to produce self-excited oscillation, the oscillation frequency f0=1/2πRC. Using double adjustable potentiometer or double adjustable capacitor can easily adjust the oscillation frequency. In the commonly used RC oscillator circuit, the high stability capacitor is generally used to switch the frequency band (coarse frequency adjustment), and then the double variable potentiometer is used to fine-tune the frequency.IV Quartz Crystal Oscillator Circuit4.1 What is a Quartz Crystal Oscillator?Quartz crystal oscillator refers to a device made on the principle that the crystal resonates due to the piezoelectric effect when the frequency of the electrical signal is equal to the natural frequency of the quartz crystal. It is a key component of crystal oscillators and narrow-band filters.Although the appearance, size and frequency of the quartz crystal oscillator are different, the structure principle is basically the same. In order to improve the stable and reliable operation of the quartz crystal, the shell components of the quartz crystal oscillator will be sealed and evacuated. Or fill with nitrogen.4.2 Quartz Crystal(1) StructureFigure17. Structure of the Quartz Crystal(2) Basic characteristicsApplying an electric field between the plates→mechanical deformation of the crystalMechanical force is applied between the plates → the crystal generates an electric fieldPiezoelectric effect: alternating voltage → mechanical vibration → alternating voltageWhen the alternating voltage frequency = natural frequency, the amplitude is the largest → piezoelectric resonanceThe natural frequency of mechanical vibration is related to the size of the wafer, and the stability is high.4.3 Quartz Crystal Oscillator CircuitThe high quality factor of quartz crystal is used to form an LC oscillator circuit.(1) Parallel Type quartz crystal oscillatorFigure18. Parallel Type Quartz Crystal Oscillator Quartz crystal works between fs and fp, which is quite a large inductance, and forms a capacitive three-point oscillator with C1 and C2. Because the Q value of the quartz crystal is very high, which can reach more than several thousand, the circuit can obtain high oscillation frequency stability.Figure19. Frequency Characteristics of Parallel Quartz Crystal Oscillator (2) Series type quartz crystal oscillatorFigure20. Series Type Quartz Crystal Oscillator Circuit The quartz crystal works at fs, which is resistive and has the smallest impedance, the strongest positive feedback, and zero phase shift, which meets the phase balance condition of oscillation.For frequencies other than fs, the impedance of the quartz crystal increases, and the phase shift is not zero, then the oscillation condition is not met, and the circuit does not oscillate.Figure21. Frequency Characteristics of Series Quartz Crystal OscillatorV Non-sine Wave Generating Circuit5.1 What is a Non-sine Wave Generating Circuit?It is composed of an integrating circuit and a hysteresis comparator circuit. The role of the integrator circuit is to produce a transient process. The hysteresis comparator acts as a switch, that is, the steady state is destroyed by the continuous closing of the switch, and a transient process is generated.Commonly used non-sine wave generating circuits include rectangular wave generating circuits, triangular wave generating circuits and sawtooth wave generating circuits, etc. They are often used as signal sources in pulse and digital systems.5.2 Rectangular Wave GeneratorIt is composed of hysteresis comparison circuit and RC timing circuit. The output has no steady state and there are two transient states; if the output is high level, it is defined as the first transient state, and the output is low level as the second transient state.Basic components:(1) Switching circuit: The output has only two situations of high level and low level, called two states; therefore, a voltage comparator is used.(2) Feedback network: self-control, when the output is in a certain state, it breeds the condition of turning into another state. Feedback should be introduced.(3) Delay link: Make the two states maintain a certain period of time and determine the oscillation frequency. Use RC circuit to achieve.Circuit composition:Figure22. Rectangular Wave Generating Circuit5.3 Triangle Wave and Sawtooth Wave Signal GeneratorThe circuit structure of the triangle wave generator: hysteresis comparator + inverting integratorworking principle:Figure23. Circuit of Triangle Wave Generator Sawtooth wave generator: change the forward and reverse charging time constant of the integrator, thereby changing the duty cycle.Figure24. Circuit Diagram of Sawtooth Generator uo1=+UZ, D is cut off, charging time constant: R4C.uo1=-UZ, D is on, charging time constant: (R6∥R4)C≈R6C.Figure25. The Waveform of the Sawtooth GeneratorVI QuizLC resonant circuits are used in:a) RF and ultrasonic oscillators.b) AF and ultrasonic oscillators.c) LF sweep oscillators.d) Variable frequency crystal oscillators. Answer: aⅦ FAQ1. What are the uses of an oscillator?Oscillators have very high precision and accuracy usually <100 ppm variation at a max. So with this kind of accuracy, the oscillator can be used as a clock of the microcontroller (the clock is the most essential part of the microcontroller, without an accurate clock, the functionality will be erratic because we cannot expect the output at the same time we have designed it for). All the quartz-based watches use an Oscillator (32kHz quartz crystal) to keep the time. SO if your timekeeping devices are running with an oscillator, you can imagine the accuracy.Oscillators can additionally be used to generate waveforms required in test benches. In almost all the applications where timing and synchronization are very essential, an oscillator finds its place. For example, in communication systems (whichever electronic communication you consider let it be a telephone, lan, anything) an oscillator is the heart.An oscillator can be used in power systems to generate accurate power waveforms. 2. What is the function of a local oscillator?A local oscillator is used in transmitters and receivers to add or subtract an amount to a basic carrier and modulation. Very handy, as it’s easiest to build up a carrier and modulate it at a low frequency, like 445Kc or 10.7MHz, and then add to it a “LO” to get it up to the FM band or the Gigahertz Wifi or radar bands. The same thing on receive, you first use a 'LO' to subtract down to an intermediate frequency where it’s so much easier to amplify and filter. 3. How do you make a crystal oscillator?The simplest is to use a logic inverter. Put a crystal between the input and output. Some schematics show some caps from the crystal legs to the ground and some show a series resistor. 4. Which type of circuit is used in the oscillator?Types of Oscillators: Harmonic Oscillators & Crystal Oscillators. Harmonic or linear oscillators produce a sinusoidal output where a signal increases and decreases at a predictable level over time. Two basic types are RC, or resistor/capacitor circuits, as well as LC, or inductor-capacitor circuits. 5. What is an Oscillator and the types of oscillators?An oscillator is a type of circuit that controls the repetitive discharge of a signal, and there are two main types of the oscillator; a relaxation, or a harmonic oscillator. This signal is often used in devices that require a measured, continual motion that can be used for some other purpose. 6. What is the basic principle of an oscillator?There are many types of electronic oscillators, but they all operate according to the same basic principle: an oscillator always employs a sensitive amplifier whose output is fed back to the input in phase. Thus, the signal regenerates and sustains itself. This is known as positive feedback. 7. What is the working of the oscillator?Oscillators convert direct current (DC) from a power supply to an alternating current (AC) signal. They are widely used in many electronic devices ranging from simplest clock generators to digital instruments (like calculators) and complex computers and peripherals etc. 8. How does an oscillator work without input?An oscillator circuit uses a vacuum tube or a transistor to generate an AC output. ... For continuously generating output without the requirement of any input from the preceding stage, a feedback circuit is used. From the above block diagram, the oscillator circuit produces oscillations that are further amplified by the amplifier. 9. What causes oscillation?If a constant force such as gravity is added to the system, the point of equilibrium is shifted. ... In the spring-mass system, oscillations occur because, at the static equilibrium displacement, the mass has kinetic energy which is converted into potential energy stored in the spring at the extremes of its path. 10. What is the difference between oscillator and inverter?The oscillator is a generalized term for an active circuit that produces a periodic waveform. The inverter is a specialized term for a system that contains an oscillator and produces large amounts of power(such as AC) from a source (like a DC battery). The oscillator has no input and produces an oscillating wave as output. 

As one of the world-leading research and innovation hub in nanoelectronics and digital technology,IMEC announced at the 2017 Symposia on VLSI Technology and Circuits that the world's first demonstration of a vertically stacked ferroelectric,AI doped HfO2 device for NAND applications.Using a new material and a novel architecture,imechas created a non-volatile memory concept with attractive characteristics for power consumption, switching speed, scalability and retention. The achievement shows that ferro-electric memory is a highly promising technology at various points in the memory hierarchy, and as a new technology for storage class memory. Imec will further develop the concept in collaboration with the world's leading producers of memory ICs.  Ferro-electric materials consist of crystals that exhibit spontaneous polarization; they can be in one of two states, which can be reversed with a suitable electric field. This non-volatile characteristic resembles ferromagnetism, after which they have been named. Discovered more than five decades ago, ferro-electric memory has always been considered ideal, due to its very low power needs, non-volatile character and high switching speed. However, issues with the complex materials, the breakdown of the interfacial layer and bad retention characteristics have presented significant challenges. The recent discovery of a ferro-electric phase in HfO2, a well-known and less complex material, has triggered a renewed interest in this memory concept.  "With HfO2, there is now a material with which we can process ferro-electric memories that are fully CMOS compatible. This allows us to make a ferro-electric FET (FeFET) in both planar and vertical varieties," noted Jan Van Houdt, imec's chief scientist for memory technology. "We are working to overcome some of the remaining issues, such as retention, precise doping techniques and interface properties, in order to stabilize the ferro-electric phase. We are now confident that our FeFET concept has all the required characteristics. It is, in fact, suitable for both stand-alone and embedded memories at various points in the memory hierarchy, going all the way from non-volatile DRAM to Flash-like memories. It has particularly interesting characteristics for future storage-class memory, which will help overcome the current bottleneck caused by the differences in speed between fast processors and slower mass memory." Imec recently presented the first, extremely positive results to its partners. The research center is now offering further development and industrialization of the vertical FeFET as a program to all its memory partners, which include the world's major companies producing memory ICs.  Van Houdt explained "FeFETs can be used as a technology to build memory very similar to Flash-memory, but with additional advantages for further scaling, simplified processing, and power consumption,with our longstanding R&D and processing experience on advanced Flash, we are uniquely positioned to offer our partners a head start in this exciting opportunity. They can then decide how best to fit ferro-electric memories in their products and chips." This is a breakthrough in CMOS-compatible ferroelectric memory, let's look forward to the CMOS-compatible ferroelectric memory together.