This filter was found in Texas Instruments documentation from the 1980s. The circuit uses a common operational amplifier and has its response curve in the figure.
MCP19124/5 Contains Independent Voltage and Current Control Loops Plus a Full Suite of...
A flash of light on one sensor or the touch of your fingers on the other type of sensor will turn...
This 1-transistor timer was published in Radio Electronics magazine in December 1960. The circuit has...