Ultra high gain FET amplifier (CB9065E)

Found in American documentation this circuit has a typical gain of 500 times. Other transistors can be used.

10 kHz Salen Key Filter (CB5193E)
This low-pass filter was found in an American publication from the 80's. The circuit uses an...
Continuity Tester (CB4546E)
This continuity tester for low resistances was found in an English magazine from 1978. The circuit...
Unity Gain Second Order Filter (CB25596E)
This low-pass filter with 741 op and symmetrical source was found in the August 1993 issue of...