This circuit is from a Radio Electronics from October 1963. The transistor is a power transistor of the time, and two transformers are used. The input has 10k impedance and is powered by 12 V.
This circuit was found in an Electronic Design from the 90s. Operational amplifiers admit modern...
The presented circuit is based on an operational transconductance amplifier (OTA) having been...
Found in an 80's documentation this circuit uses an integrated from the uncommon era today. Other...