Based on the Linear Technology LTC2054, this -48 V circuit was found in a 2005 manual. The circuit is powered with 5 V and can be used as a shield.
This circuit, which can serve as a reference for restorations, was found in the October 1989 issue...
We found this circuit in a publication for radio amateurs of 1976. The operational amplifier is a...
This dual-LED circuit indicates three signal levels. It was found in the January 1996 issue of...