This circuit was found in a 1980s documentation for amateur radio. The circuit makes use of components of the era, but modern equivalents can be used.
This circuit is from a1970 documentation. R1 may have 10k and P1 47k. The transistors can be BC558...
In the figure we have an amplifier using the 741 operational amplifier without the need for a...
This filter was found in old Raytheon documentation. The circuit makes use of operationals of the time, but...