This circuit was obtained from a Philips documentation from 1968. The transistors can be replaced with equivalents, only with care so that the doubles are exchanged for matched pairs.
This circuit was obtained in a 1973s documentation. The transistors may be BC558 for the PNP and...
Found in a 90's EDN this circuit can be used as a shield. The transistor is a general-purpose type and the...
This circuit was found in a 1980s Intersil documentation. The integrated circuit used is not...