This circuit for audio applications was found in an English magazine from the 80's. The circuit has a pass band below 3 kHz making it ideal for telecom applications.
This circuit provides a constant current of 1 mA, stabilized by an LED, which can be equivalent to that...
This receiver for the mid-wave band was found in a documentation from the 60's. The transistors are made...
This circuit converts a positive CMOS supply voltage to a negative one. We found it in a 90s...