Based on the LF256 operational amplifier, this circuit was found in the September 1989 issue of Radio Electronics magazine. The indicator is analog, and the power supply must be symmetrical.
Found in an Electronics Now from the 90s, this circuit with the 555 generates a signal with 50%...
Frequencies from 1 to 10 MHz can be obtained with a small adjustment of the variable in a narrow...
This is a multi-component tester with visual indication by LED and polarity selection in the test....