Tone-controlled microphone amplifier (CB20806E)

This circuit was found in American documentation from the 1980s. The integrated circuit used is still common today, but equivalents can be used.

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Sequential unijunction timer (CB10190E)
This circuit with unijunction transistors was found in a documentation from the 80's. The trigger...
Video driver with impedance matching (CB20915E)
In this circuit of an old American documentation, the input impedance is the same as the output...
18 V Voltage Doubler (CB20180E)
In the figure we have the way to obtain a voltage of 18 V from a 6.3 V transformer with central...