This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V battery drops below 7 V. The transistors can be BC548.
The amplifier gain shown in the figure is given by R1. The circuit is valid for other photodiodes and is...
In the figure we have the way to excite a lamp up to 600 mA with one of the four operating LM324....
With a 22 V symmetrical power supply this amplifier provides 15 W of output power with excellent...