We found this simple circuit in December 1975 Radio Electronics magazine. The integrated circuit is the 4009 CMOS, and the circuit works in both TTL and CMOS depending on the power supply.
This filter, from an audio publication from 1977, passes the frequency range corresponding to the...
In the figure we have three voltage doubler configurations that can be used in high and low...
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...