This very low frequency circuit was found in a 1964 Electronic Design. Transistors may be modern equivalents. The filter is low pass type.
In the figure we have the way to use an operational amplifier on a higher voltage source than it...
This configuration is from a 1964 US documentation valid for any FET. The range of power voltages...
This circuit uses na Unijunction Transistor (UJT) to produce a modulation tone for several...