We found this precision circuit in a manual from the 80's. The operational amplifier is of a common type at the time, and equivalents can be tested. Transistors are general purpose types.
This circuit was found in a 1992 PE Hobbyst. The circuit detects the presence of spy...
This circuit is from an old American publication from 1977. Transistor Q1 can be a TIP42 and Q2 a...
This circuit reverses the signal if both positive and negative. We found it in an American...