This commercial transistor radio was manufactured by RCA in the 1960s. The circuit has only 4 transistors and is powered by a voltage of 9 V with an audio power of 20mW.
The interesting circuit shown in the figure, can have its gain digitally controlled and present two...
This circuit that has a response from 10 Hz to 700 kHz was found in Philips documentation from 1968. Dual...
This circuit is from a 1976 Motorola CMOS manual. It can be implemented with modern Darlingtons like...