This filter has the components calculated for the frequency of 1 kHz but can be changed. The input resistor can be 100k and the source symmetrical. Any operational amplifier can be used.
This transmitter, found in Raytheon documentation from 1957, has a range of a few meters. L1 can...
This circuit is from Ferranti documentation from 1967. The operational is of the time, but the...
This circuit was found in the May 1989 issue of Radio Electronics magazine. The circuit requires a...