The integrated circuit used in this 2002 project is not very common. It is powered directly by the telephone line, requiring no power supply.
This amplifier for automotive use is from the Philips Databook of 1990. The integrated circuit must...
This fast-acting circuit uses any phototransistor as a sensor. The circuit drives a 30 V relay, but...
With this 1-transistor circuit we have a high input impedance and good gain. The circuit is from a...