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.
We found this circuit in a publication on operational amplifiers from 1978. The circuit is made...
This circuit was found in a Philips documentation from 1970. The components are of the time,...
Found in a 1967 documentation this circuit can be applied to any operational amplifier. Components...