Found in a Popular Electronics from the 90s, this circuit uses common components with several operational options, including the use of an optocoupler that allows its application in a shield.
This version of the Pierce oscillator with the 2N3904 was found in the January 1994 issue of...
The traditional configuration of a non-inverting amplifier with the operational 741 shown in the...
This circuit is from a Radio Electronics from January 1958. The transistor is the CK722, and the...