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.
The coil can be formed by 100 turns of 26 or 28 wire on a ferrite rod in this medium wave radio...
This circuit is from a 1968 Electronic Design. The characteristics of the output transformer are not...
This circuit is from a 1970 publication, having been implemented with germanium PNP transistors. We can...