Catalog Description Features Schematic Absolute Maximum Ratings Electrical / Optical Characteristics H21A2 Datasheet H21A2 Manufacturer Using Warning H21A2 FAQ   Description The H21A1, H21A2 and H21A3 consist of a gallium arsenide infrared emitting diode coupled with a silicon phototransistor in a plastic housing. The packaging system is designed to optimize the mechanical resolution, coupling efficiency, ambient light rejection, cost and reliability. The gap in the housing provides a means of interrupting the signal with an opaque material, switching the output from an “ON” to an “OFF” state.   Features Opaque housingLow cost035” aperturesHigh IC(ON)   Schematic Figure: H21A2 Schematic 1.Derate power dissipation linearly 1.33 mW/°C above 25°C. 2.RMA flux is recommended. 3.Methanol or isopropyl alcohols are recommended as cleaning agents. 4.Soldering iron tip 1/16” (1.6mm) minimum from housing.   Absolute Maximum Ratings (TA = 25°C unless otherwise specified) ParameterSymbolRatingUnitOperating TemperatureTOPR-55 to +100°CStorage TemperatureTSTG-55 to +100°CSoldering Temperature (Iron)TSOL-I240 for 5 sec°CSoldering Temperature (Flow)TSOL-F260 for 10 sec°C INPUT (EMITTER)  Continuous Forward Current IF50mAReverse VoltageVR6VPower DissipationPD100mW OUTPUT (SENSOR)  Collector to Emitter Voltage VCEO30VEmitter to Collector VoltageVECO4.5VCollector CurrentIC20mAPower Dissipation (TC = 25°C)PD150mW   Electrical / Optical Characteristics  (TA =25°C)(All measurements made under pulse condition) PARAMETERTEST CONDITIONSSYMBOLDEVICESMINTYPMAXUNITS INPUT (EMITTER)         Forward Voltage IF = 60 mAVFAll——1.7VReverse Breakdown VoltageIR = 10 μAVRAll6——VReverse Leakage CurrentVR = 3 VIRAll——1µA OUTPUT (SENSOR)       Emitter to Collector Breakdown IF = 100 μA, Ee = 0BVECOAll6——VCollector to Emitter BreakdownIC = 1 mA, Ee = 0BVCEOAll30——VCollector to Emitter LeakageVCE = 25 V, Ee = 0ICEOAll——100nA COUPLED                             On-State Collector Current IF = 5 mA, VCE = 5 VIC(ON)H21A10.15——mAH21A20.3——H21A30.6——IF = 20 mA, VCE = 5 VH21A11——H21A22——H21A34——IF = 30 mA, VCE = 5 VH21A11.9——H21A23——H21A35.5——Saturation VoltageIF = 20 mA, IC = 1.8 mAVCE(SAT)H21A2/3——0.4VIF = 30 mA, IC = 1.8 mAH21A1——0.4VTurn-On TimeIF = 30 mA, VCC = 5 V, RL = 2.5 KΩtonAll—8—µsTurn-Off TimeIF = 30 mA, VCC = 5 V, RL = 2.5 KΩtoffAll—50—µs   Figure: Output Current vs. Input Current     Figure: Output Current vs. Temperature     Figure: VCE(SAT) vs. Temperature       Figure: Leakage Current vs. Temperature     Figure: Switching Speed vs. RL     Figure: Output Current vs. Distance   H21A2 Datasheet You can download the datasheet from the link given below: H21A2 Datasheet   H21A2 Manufacturer Onsemi is driving energy efficient innovations, empowering customers to reduce global energy use. The company offers a comprehensive portfolio of energy efficient power and signal management, logic, discrete and custom solutions to help design engineers solve their unique design challenges in automotive, communications, computing, consumer, industrial, LED lighting, medical, military/aerospace and power supply applications. onsemi operates a responsive, reliable, world-class supply chain and quality program, and a network of manufacturing facilities, sales offices and design centers in key markets throughout North America, Europe, and the Asia Pacific regions.   Using Warning Note: Please check their parameters and pin configuration before replacing them in your circuit.   H21A2 FAQ What is an optical interrupter? An opto-interrupter is like a tiny trip line, when something solid passes between the emitter and the receiver it is detectable as a change in the digital output. These are great for making very low cost rotary encoders and optical end stops.   How does an opto switch work? When an object is moved into the slot between the LED and phototransistor the light is interrupted and the phototransistor switches off. Opto activated switches are normally operated in saturation mode to provide definite on and off signals.   What is a phototransistor? A phototransistor is a bipolar or unipolar transistor where light can reach the base, creating optically generated carriers. This modulates the base-collector junction resulting in an amplified current through transistor action, which can lead to much greater photosensitivity.