The original purpose of this circuit, which we find in old American documentation, is to modulate an RF carrier for telecommunications applications. Transistors support equivalents.
This circuit is a driver for R-2R network of AD converters. We found it in manufacturer...
This circuit was found in an American publication from the 60's. The transistor is made of...
This circuit produces an audio tone on the speaker or magnetic capsule. Rx must be such that added...