Found in an English publication from the 1980s, this circuit can be built with equivalent transistors such as the BC549. The signal must be applied to an external amplifier.
The filter shown in the figure, suggested by Motorola, operates at a cut-off frequency of 1 kHz,...
This circuit uses an unusual operational amplifier nowadays and has a very low consumption. The...
In this circuit R1 has 2M5, R2 and R3 are 5M obtaining a detection current for the diode of 0.5...