We found this circuit with transistors in a Philips documentation from 1968. The double transistor can be replaced by discrete married types. The power supply is symmetrical.
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...