Transistor Amplifiers continued 3

Symmetric design became an issue during the 1960's, when the designs started having +/0/- powerrails. Below you can see some amps on that issue: Below a Jean Hiraga design, Hiraga still used some early Japanese transistors, but also the better, specially for audio designed series, like the legendary 2SC1775 and its complementary. Nowadays the power transistors can be replaced by high speed modern ones, but in that case the high cut-off frequency is to be influenced with some cut-off capacitors.

Another Hiraga design with a different approach below:

A full symmetric amplifier from 1975 by Radio Electronics, still using early power transistors:

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©Hans Hilberink PE1MMK 30-09-2001.