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.
We found this configuration in a 70s American documentation. The circuit makes use of operational...
The circuit shown is powered by 5 V and was suggested by Motorola's Linear Databook of 1990....
This simple transistorized intercom circuit was found in a 2000 documentation. It can be powered by a...