This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V batteries since it requires a symmetrical source.
This is a rectifier for small intensity signals, and equivalent operational amplifiers can be...
This circuit was obtained from a 1969 Electronic Design. Transistors admit modern equivalents. The frequency...
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...