This circuit was found in an American publication from 1968. The transistors are from the time, but it can be made from modern transistors.
We found this circuit in a 2005 Linear Technology manual. Observe the component values and...
We found this circuit in a 1967 El3ectronics World. The transistors are from the era but can be...
This 1/2 hertz high selectivity filter was found in the December 1990 issue of Radio Electronics...