This old 1967 audio preamp uses germanium transistors. It was found in Japanese documentation at the time and has a gain of 70 dB, being powered by p V. The input sensitivity is only 12 mV.
This configuration is also valid for other operators and the formula for calculating the gain is...
This inductively coupled oscillator was found in an American documentation from the 90's. The...
This circuit was obtained from an Analog Devices manual from the 90's. The integrated circuit is...