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AD620 Instrumentation Amplifier: Pinout, Circuit, Parameters [FAQ]

  • Contents

AD620 is a low cost, high accuracy instrumentation amplifier that requires only one external resistor to set gains of 1 to 10,000.

 

This blog covers AD620 amplifier pinout, datasheet, equivalent, features, and other information on how to use and where to use this device.


Catalog

AD620 Introduction

AD620 Pinout

AD620 Basic Parameters

AD620 Features

AD620 Applications

Where to use AD620 amplifier?

How to use AD620 amplifier?

AD620 Package

AD620 Application Circuit

AD620 Working Principle

AD620 Alternative Models

AD620 Manufacturer

FAQ

Ordering & Quantity


AD620 Introduction

ADI’s AD620 comes in 8-lead SOIC and DIP packages and are low-cost, high-accuracy instrumentation amplifiers that, with an external resistor, allow the user to set gains of 1 to 10,000. The small footprint design and low power consumption (only 1.3 mA (maximum) supply current) make it a good fit for portable or remote applications that require a battery.

 

The AD620, with its high accuracy of 40 ppm (maximum) nonlinearity, low offset voltage of 50 µV (maximum), and offset drift of 0.6 µV/°C (maximum), is ideal for use in precision data acquisition systems such as weigh scales and transducer interfaces. Furthermore, the low noise, low input bias current, and low power of the AD620 make it well suited for medical applications such as ECG and noninvasive blood pressure monitors.

 

The low input bias current of 1.0 nA (maximum) is made possible with the use of Superϐeta processing in the input stage. The AD620 works well as a preamplifier due to its low input voltage noise of 9 nV/√Hz at 1 kHz, 0.28 μV p-p in the 0.1 Hz to 10 Hz band, and 0.1 pA/√Hz input current noise. Also, the AD620 is well suited for multiplexed applications with its settling time of 15 μs to 0.01%, and its cost is low enough to enable designs with one in-amp per channel.


AD620 Pinout

The datasheet provided above is for your reference, so that you can understand the physical dimensions of all packages in more detail. The configuration of all 8 pins and the function of each pin are as follows:

ad620 pinout

 

The function of all 8 pins are as follows:

Pin Number Pin Name Description
1 Gain (Rg) Inverting Gain Terminal connected to a resistor to set gain value
2 Inverting Input (IN-) The Inverting input pin of the Op-Amp
3 Non- Inverting Input (IN-) The Non - Inverting Input Pin of Amplifier
4 Power (-Vs) Negative supply terminal
5 Reference Output reference input. Normally connected to common
6 Output Amplifier output pin
7 Power (+Vs) Positive supply terminal
8 Gain (Rg) Non - Inverting Gain Terminal connected to resistor to set gain value

AD620 Basic Parameters

Parameters AD620A AD620B AD620S
Gain Range 10,000 10,000 10,000
Gain Error G=1 (%) 0.10 0.02 0.10
Gain Error G=1000 (%) 0.7 0.5 0.7
Input Offset (µV) 125 50 125
Input Bias current (nA) 2.0 1.0 2.0
Input Offset Current (nA) 1.0 0.5 1.0
Input Voltage Range (V) + -1.2 + -1.2 + -1.2
Input offset current (nA) 200 50 500
Input Impedance Differential Common Mode (GΩ_pF) 10II2 10II2 10II2
Common Mode Rejection Ratio G=1 (dB) 90 90 90
Common Mode Rejection Ratio G=1000 (dB) 130 130 130
Slew Rate (V/µs) 1.2 1.2 1.2
Small Signal -3dB Bandwidth G=1 (kHz) 1000 1000 1000
Small Signal -3dB Bandwidth G=1000 (kHz) 12 12 12
Settling Time to 0.01% G= 1-100 (µs) 15 15 15
Settling Time to 0.01% G= 1000 (µs) 150 150 150
Input Voltage Noise (nV/ Hz) 13 13 13
Output Voltage Noise (nV/ Hz) 100 100 100
Reference Input Resistance (kΩ) 20 20 20
Reference Input Current (µA) 60 60 60
Reference Input Voltage Range (V) + -1.6 + -1.6 + -1.6
Output Short Circuit Duration Indefinite Indefinite Indefinite
Lead Temperature Range for 10sec soldering (°C) 300 300 300
Operating Temperature Range (°C) -40 to +85 -40 to +85 -55 to +125

AD620 Features

  • EASY TO USE

  Gain Set with One External Resistor

  (Gain Range 1 to 10,000)

  Wide Power Supply Range (±2.3 V to ±18 V)

  Higher Performance than Three

  Op Amp IA Designs

  Available in 8-Lead DIP and SOIC Packaging

  Low Power, 1.3 mA max Supply

  • LOW NOISE

  9 nV/√Hz, @ 1 kHz, Input Voltage Noise

  0.28 µV p-p Noise (0.1 Hz to 10 Hz)

  • EXCELLENT DC PERFORMANCE (B GRADE)

  50 µV max, Input Offset Voltage

  0.6 µV/°C max, Input Offset Drift

  1.0 nA max, Input Bias Current

  100 dB min Common-Mode

  Rejection Ratio (G = 10)

  • EXCELLENT AC SPECIFICATIONS

  120 kHz Bandwidth (G = 100)

  15 µs Settling Time to 0.01%


AD620 Applications

  • Weigh scales

  • ECG and medical instrumentation

  • Transducer interface

  • Data acquisition systems

  • Industrial process controls

  • Battery-powered and portable equipment


Where to use AD620 amplifier?

The AD620, with its high accuracy of 40 ppm maximum nonlinearity, low offset voltage of 50 μV max, and offset drift of 0.6 μV/°C max, is ideal for use in precision data acquisition systems, such as weigh scales and transducer interfaces. Furthermore, the low noise, low input bias current, and low power of the AD620 make it well suited for medical applications, such as ECG and non-invasive blood pressure monitors.


How to use AD620 amplifier?

The AD620 only requires a resistor to set its gain value and can therefore be easily set up. The most basic commonly used circuit for AD620 is shown below.

how-to-use-ad620-amplifier

The IC is powered by pin 7 and pin 4 is connected to the ground. Here I used a single supply of +5V. The non-inverting pin (pin 2) and the inverting pin (pin 3) are connected to the signal to be amplified or compared on the basis of the Op-Amp application. The reference pin (pin 5) is normally grounded along with pin 4, the reference pin is used to direct the output to the voltage when the difference voltage between the inverter and the non-inverter pin is 0V.

 

The Gain of the Op-Amp can be set simply by connecting the correct resistance value to the pin +Rg (pin 8) and the pin –Rg (pin 1). Here I have connected a resistor with a value of 500, which will set the Op-Amp to a gain value of 100. The formulas used to calculate the gain value from R have been given below.

G = (49.4 k/RG) + 1


AD620 Package

ad620 package

ad620 package

ad620 package


AD620 Application Circuit

ad620 circuit

ad620 circuit

ad620 circuit


AD620 Working Principle

ad620 working principle

The AD620 is a monolithic instrumentation amplifier based on a modification of the classic three op amp approach. Absolute value trimming allows the user to program gain accurately (to 0.15% at G = 100) with only one resistor. Monolithic construction and laser wafer trimming allow the tight matching and tracking of circuit components, thus ensuring the high level of performance inherent in this circuit.

 

The input transistors Q1 and Q2 provide a single differentialpair bipolar input for high precision (Figure 36), yet offer 10× lower input bias current thanks to Superϐeta processing.

 

Feedback through the Q1-A1-R1 loop and the Q2-A2-R2 loop maintains constant collector current of the input devices Q1 and Q2, thereby impressing the input voltage across the external gain setting resistor RG. This creates a differential gain from the inputs to the A1/A2 outputs given by G = (R1 + R2)/RG + 1. The unity-gain subtractor, A3, removes any common-mode signal, yielding a single-ended output referred to the REF pin potential.

 

The value of RG also determines the transconductance of the preamp stage. As RG is reduced for larger gains, the transconductance increases asymptotically to that of the input transistors. This has three important advantages: (a) Open-loop gain is boosted for increasing programmed gain, thus reducing gain related errors. (b) The gain-bandwidth product (determined by C1 and C2 and the preamp transconductance) increases with programmed gain, thus optimizing frequency response. (c) The input voltage noise is reduced to a value of 9 nV/√Hz, determined mainly by the collector current and base resistance of the input devices. The internal gain resistors, R1 and R2, are trimmed to an absolute value of 24.7 kΩ, allowing the gain to be programmed accurately with a single external resistor. The gain equation is then

 


AD620 Alternative Models

  • AD8422

Higher BW at 1/3 the power, with RRO and OVP (same pinout as AD8221)


AD620 Manufacturer

Analog Devices (NASDAQ: ADI) is a world leader in the design, manufacture, and marketing of a broad portfolio of high performance analog, mixed-signal, and digital signal processing (DSP) integrated circuits (ICs) used in virtually all types of electronic equipment. Since established in 1965, ADI have focused on solving the engineering challenges associated with signal processing in electronic equipment. ADI currently produce a wide range of innovative products—including data converters, amplifiers and linear products, radio frequency (RF) ICs, power management products, sensors based on microelectromechanical systems (MEMS) technology and other sensors, and processing products, including DSP and other processors—that are designed to meet the needs of our broad base of customers.


Component Datasheet

AD620 Datasheet


FAQ

  • What is AD620?

AD620 is a low-cost, high-precision instrumentation amplifier. It only requires an external resistor to set the gain. The gain range is 1 to 10,000.

  • Can I change AD620 to AD623 when making MCU products?

Both AD620 and AD623 are single instrumentation amplifiers, and the pin arrangement is exactly the same.

The main difference is: AD620 must use positive and negative power supplies, AD623 can be a positive and negative power supply or a single power supply.

If the original board is AD620, you can replace it with 623; if the original board is AD623, you may not be able to replace it with 620 (it depends on whether the power supply of the original board circuit is dual power supply or single power supply).

After replacing AD620 and AD623 in single-chip products, the program can work normally without modification.

  • What is the difference between AD620BR and AD620AN?

Their packages are different.

  • What is the output resistance of AD620? How to adjust it?

AD620 is a kind of low power consumption instrument amplifier, its output resistance is about 10K, this is the inherent characteristic of this chip, generally it is difficult to adjust.

If you have requirements for output resistance, you can generally use an external circuit to solve it.

  • Is AD620 a positive phase amplification or a reverse phase amplification?

AD620 is an instrument amplifier, the output voltage is [(Vin+)-(Vin-)]*gain.

If the desired signal is (Vin+)-(Vin-), the gain is positive, which is equivalent to positive amplification.

Conversely, if the desired signal is (Vin-)-(Vin+), the gain is equivalent to negative, which is equivalent to reverse amplification.

  • What is an instrumentation amplifier?

Instrumentation amplifier, an improvement of the differential amplifier, has an input buffer, does not require input impedance matching, so that the amplifier is suitable for measurement and electronic instruments

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