This circuit is from the Motorola Linear Databook of 1990 and can be implemented with other operational amplifiers. The power supply must be symmetrical.
The integrated circuit can be any operational and T1 can be a BC548 and T2 a TIP41 in this circuit of a...
We can make an oscillating relay producing a rectangular signal taking advantage of the inductance of...
We find this circuit in an old American documentation, but it is perfectly current by its...