Stereo preamplifier (CB8510E)

Found in a 90s Popular Electronics, this circuit is based on a uA739, an unusual component today.

Transistor testing center (CB23768E)
We found this test circuit in a March 1967 Radio Electronics. The circuit uses a zener-regulated supply and...
Booster for cassette player (CB22151E)
This amplifier for small cassette tape players was found in an English documentation from 1969. The...
High Side Current Sensor LTC6800 (CB5221E)
We found this circuit in a 2005 Linear Technology manual. The resistor is calculated for the...