Freeze Alarm (CB14454E)

The circuit of a 1968 publication can be implemented with more modern transistors such as BC548 for NPN and BC558 for PNP.

Frequency Doubler (CB13736E)
This circuit was obtained in a 1975 documentation. The maximum frequency depends on the diodes and the...
AC Gain 10 Amplifier LM3900 (CB19120E)
In the figure we have the basic configuration of an operational amplifier for AC signals using the...
Signal Injector (CB1385E )
This traditional signal injector from a 1970s publication uses germanium transistors. We can mount it...