We found this circuit in a 1976 documentation. The FET can be BF245 or MPF102 and the power supply need not be symmetrical. The FET in the feedback acts as an automatic gain control.
The integrated circuit of this project found in an American publication from the 70's is not very...
The CUT frequency for this filter is determined by the capacitors. The µA4138 is a quad version of...
In the figure we show how to supply a DC motor from 6 to 12 V with alternating current. The diodes...