This detector with ultra-low deviation was found in an American documentation from the 90s. Operational amplifiers are from that time. The power supply must be symmetrical.
This circuit was obtained from Linear Applications Handbook from National Semiconductor of 1994. It...
This circuit is from a 1974 publication, but it can still be easily assembled today with BC548...
This short-range, medium-wave transmitter was found in a 1966 documentation. The transistors are...