- on Test & Measurement
- Published in issue 7/2010 on page 18
(Summer Circuits 2010 article)
This crystal tester is very straightforward. Fitting a crystal or switching on the supply voltage generates a ‘start pulse’ resulting from the fact that the crystal briefly pulls the voltage on the base of T1 low. This directly affects the operating point of the transistor via feedback capacitor C1, with the result that the transistor starts oscillating.