We found this circuit in the Linear Applications Handbook by National Semiconductor. The circuit is from 1994, but it can be made with more modern equivalent components.
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...