Suggested by Siliconix in documentation from the 90s, this amplifier has its gain digitally selected. The components are from that time, not easy to find today.
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...