The selected circuit is from the Texas Instruments optoelectronics manual. With it you can receive optical signals in CW. Transistors support equivalents.
This circuit is from a Radio Electronics from October 1963. The LDR and transistors are from the...
The figure shows how to use an operational circuit as a voltage divider. The circuit is from a...
This is the basic configuration of an operational amplifier as a current regulator. We found it in...