This circuit is from American documentation from the 70s. The circuit makes use of the operating system of the time, but it can be implemented with more modern equivalents.
This proximity sensor circuit is from an 80's documentation. The used integrated circuits are...
This current boosting circuit uses an op-amp and 3 transistors. The current depends on Q1. The...
In the figure we have the circuit of a clamp-type microammeter described in the Radio Electronics...