With this circuit found in an American documentation from 1969 it is possible to vary the selectivity (Q factor) of a tuned circuit. The operational is from that time.
This circuit is from a 2005 Linear Technology application manual. The circuit uses a commercial...
We found this circuit in an English publication from 1982. The power MOSFET can be of any type and the...
We found this circuit in a 1982 documentation. An intercom to be good must be sensitive and have...