This variable filter circuit was found in July 1975 Radio Electronics magazine. The circuit uses 3 general purpose op-amps like the 741 and must use a symmetrical source.
A The adjustable Q-factor rejector filter in the figure is based on two LM110. These integrated...
This circuit can be powered by a voltage of only 2.5 V. Next to the diagram we have the formulas...
This circuit with a supply voltage of only 2.5 V was found in a 2005 Linear Technology...