Using an LDR as a sensor, this circuit is from the Radio Electronics magazine of December 1984. The operational amplifier is the 741 and the source must be symmetrical.
This amplifier uses common transistors in a phase inverter configuration. Transistors must be...
This is the same amplifier circuit as the previous circuit adapted to operate with a single...
In fact, this 1994 circuit uses a scale of LEDs to indicate the pulse rate applied to its input....