This circuit was found in a 1965 Electronic Design. Transistor Q2 must be load dependent. The circuit can be adjusted for currents from 1 to 10 A. The voltage drop is 3 V and the maximum voltage is 35 V.
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals...