This circuit consists of two stages that each shift 180 degrees the signal. The circuit was proposed by Siliconix in a 1966 publication. Equivalent FETs can be used.
This circuit is from a 1995 technical documentation. The transistor can be a BC558 and the sensor...
Found in a Popular Electronics from the 90s, this circuit checks the presence of voltage on a...
The critical component of this amplifier is the output transformer. We found the circuit in an old...