This circuit was obtained from Dutch documentation from 1964. The components are of the time, but current equivalents such as BC548 to BC108 can be used.
This interesting bandpass filter using an operational amplifier 741 has its cutoff frequency...
We found this circuit with duty cycle adjustment in the May 1988 Radio Electronics magazine. The...
In the figure we have a constant current source for Shape Memory Alloy or (Nitinol). The value of...