Found in 1965 Delco Radio documentation, this circuit uses transistors from that era. Modern equivalents can be used. The characteristics of the inductor were not given.
The figure below shows an AC transconductance amplifier with the National Semiconductor LM3900. The...
This common circuit using operational amplifiers was found in the 1993 issue of Radio Electronics Special...
This circuit provides a voltage at the output only when the input voltage exceeds a value that...