Found in Maxim's documentation from the 90's, this circuit uses an integrated from the time providing a 12 V output from 10 to 12 V inputs.
This heartbeat sensor circuit was found in the July 1992 issue of Radio Electronics magazine. The...
This amplifier circuit with a low power MOSFET was found in Popular Electronics from the 90s. The...
This circuit, which can be built with several CMOS gates, was found in the March 1996 issue of...