Using an operational amplifier of the time, this circuit was obtained from a 90s Radio Electronics. The circuit covers the frequency range from 2 Hz to 20 kHz.
The sensor of this circuit can be any phototransistor and the SCR can be the TIC106. The circuit and...
This circuit is from a Radio Electronics from 1950. The transistor was still new and called a...
This circuit was found in a Linear Technology documentation from the 90's. The integrated circuits are...