This circuit is from the National Semiconductor's Linear Applications Handbook of 1994. The circuit can be implemented with equivalent operational. The detected voltage is given by the diode.
The frequency of this oscillator depends on the crystal used and the transistors. The circuit was...
This circuit is for collectors. It is the circuit of one of the most popular transistor radios of the...
Another of the many tachometer circuits we have on our site. This one is from the September 1976...