This circuit was found in documentation from the 1970s. However, it can be implemented with modern transistors such as 2N2222 for Q1 and BF494 for Q2. The crystal depends on the desired frequency.
This circuit is from a Harris Semiconductor datasheet from the 80s. However the circuit can be...
The purpose of this circuit is to amplify the signal of a medium or high impedance microphone,...
Medium and high power partially burned can be used as diodes in a simple Power supply as shown in...