Suggested by Radio Electronics from the 90s, this circuit is suitable for NiCAd batteries with a low battery indicator and a charge indicator.
This circuit uses two Raytheon RC4558 operational amplifiers that are similar to the 741. The...
In the figure we have the way to obtain 500 gain from a FET. FETs can be BF245 or MPF102. The...
This circuit generates an FM signal of 4.7 or 10.7 MHz for audio signals on analog TV or FM, with...