Suggested by Siliconix in documentation from the 90s, this amplifier has its gain digitally selected. The components are from that time, not easy to find today.
This circuit using an operational amplifier was found in old American documentation. It can be...
If the circuit oscillates, emitting sound, it is because the transistor is good. This simple...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...