Variable regulator with crowbar protection (CB21189E)

This circuit was found in a Popular Electronics from the 90's. The power transistors must be equipped with a heat sink.

MOSFETs bias (CB6962E)
In the figure we have a typical polarization circuit for MOSFETs with a high impedance...
Graphic Equalizer (CB24554E)
This equalizer was found in the May 1978 issue of Radio Electronics magazine. The component values...
Colpitts Harmonic Oscillator (CB9645E)
Found in a 1980s American documentation, this crystal-controlled oscillator generates 100 MHz...