We found this circuit in the Linear Applications Handbook of the 1994 National Semiconductor. The transistor must be a high voltage type and the LM3900 power supply must be symmetrical.
This light-controlled circuit uses a 6 V or 12 V relay depending on the supply. The transistor can be the...
This circuit was found in the March 1999 issue of Electronics Now magazine. The meter is analog and...
This preamp with a transistor for turntables with crystal capsules was found in a Japanese...