This circuit found in an American documentation from 1964, alters the duration of a pulse and can operate at frequencies up to 10 MHz. The transistors are from that time.
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
The adjustment of the maximum load voltage is made in the trimpot. The circuit is from 1994...
In the figure we have the conventional configuration of a differential amplifier with the...