Infra-red Emitter/Sensor Axl (LIR121)

Photo Reflector

Combined infrared emitting diode and phototransistor in one package.
Power output 1.8mW/steradian typical at IF = 20mA.
View package from front with beveled corner at top right, then top left lead is cathode (pin1), top right lead is anode (pin 2), lower left lead is collector (pin 3), lower right lead is emitter (pin 4).
Standard circuit with 5V power supply: connect pin 3 to 5V, connect base of external transistor (TR1) to pin 4, collector of TR1 to 5V, emitter of TR1 to output, connect a 160R resistor between pin 2 and 5V, and connect a 20k resistor between output (emitter of TR1) and pin 1.

Specifications based on this circuit with reflector 1mm from front of device.

Specifications
Forward voltage at IF = 20mA: 1.7V
Collector emitter breakdown voltage: 12V (Ice = 1mA)
Photocurrent (out of pin 4): 230uA min.
Saturation voltage (pins 3 to 4): 0.4V max.
Dark current (at pin 4): 100uA max.
Rise time: 1ms
Fall time: 1ms
Package size: 2.7mm x 3.4mm x 1.5mm thick.