This circuit generates short pulses. The transistor can be a 2N2222 or BC548 and the frequency is given by the resistors and the capacitor that can be changed.
We found this circuit in an old documentation, using an operational of the time. The circuit...
This circuit shows how to use a 3-terminal voltage regulator as a low frequency oscillator by...
The circuit bellow uses two NPN transistor to drive heavy loads up to some amperes. The maximum...