Both the operational amplifier and the diodes admit equivalents in this circuit suggested by National Semiconductor. The power source must be symmetrical, and the circuit curve resembles an ideal diode.
This variable filter circuit was found in July 1975 Radio Electronics magazine. The circuit uses 3...
The transistors of this circuit found in a 1965 magazine can be the BC558 and the sensitive 12 V x...
We found this circuit in a Radio Electronics from October 1965. The pickup coil can be of the...