What is the function of 741 operational amplifier in the circuit below? This is a light detector circuit.
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Except for a couple of details. The 100k resistor is too high in value to saturate the 2N2222. If you make it low enough to guarantee saturation, the 741 output will never go low enough to guarantee that the 2N2222 will turn off reliably.Tthe 741 is used as a voltage comparator. It compares the voltages at pins 1 and 3. If the voltage at pin 2 is less than the voltage at pin 3, pin 6's voltage goes toward Vcc and turns on the Q1. If the voltage at pin 2 is more than the voltage at pin 3, pin 6's voltage goes toward ground and turns off the Q1.
Ken
by Duane Benson
by Duane Benson
by Aaron Carman