Of course, the current is extremely small, but a voltage of 300 V can be obtained from 9 V of a battery. The circuit is from an Electronics Now of May 1994. C1 adjusts the operating point.
This simulation shows how to use an operational amplifier as a voltage comparator. The sample uses the...
This circuit automatically activates the relay when the phone is answered, closing the record...
This car alarm was found in an American '80s documentation. The circuit automatically activates...