This current boosting circuit uses an op-amp and 3 transistors. The current depends on Q1. The circuit is from the 1995 Encyclopedia of Electronic Circuits Volume 5.
Found in a Maxim documentation from the 1990s, this current-sensing amplifier uses components from the...
We found this circuit in a 1982 documentation. An intercom to be good must be sensitive and have...
This circuit is from a 1980s documentation, but the configuration can be applied to most modern...