In the figure we have the basic configuration of an operational amplifier for audio signals. The circuit is from a Radio Electronics from the 90s. The power supply must be symmetrical.
This circuit was found in a 1967 Raytheon manual. The transistors are from the time. Equivalent modern...
This circuit was published in a 1979 magazine, but it can still be easily assembled as the...
The circuit presented generates short pulses. This configuration was found in a publication from...