This circuit was obtained from an American 1980s documentation. The frequency depends on the crystal and the circuit may be a PNP that reaches the generated frequency.
The Buck-type DC-DC converter (voltage lowerer) shown in figure 11 is suggested by Analog Devices...
This circuit, which appears in other versions on this website, was obtained in old documentation. The load...
This circuit is from an Electronic Design from the 90's. The main integrated circuit is uncommon...