symmetrical harmonic oscillator

5 symmetrical harmonic oscillator The remarkable thing about this oscillator is not that it operates on the third overtone of a crystal nor that it is symmetrical, but that it does not use a tuned circuit. Os- cillators without tuned circuits normally operate on the funda- mental crystal frequency: as loon as it is required to work on har- monics, a tuned circuit becomes necessary to resonate at the desired BF 494 500 mv„p R7 ICI R8 C 00 R6 R5 Ti TO BF494 rz C3C1 C4 CSIII isp isp- BF 494 494 40p dal J Al R2 C R3 C2 R4 CEB ° overtone. The circuit described is reminiscent of an astable multivibrator, but it uses a novel way of connecting the crystal: between the emitters of the two transistors and in series with a small trimmercapacitor (C5 = 40 pF) It is the trimmer which enables the tuning of the oscillator to the fun- damental as well as to the third harmonic of the crystal. The circuit has been designed for crystals with a fundamental fre- quency of 6 ... 20 MHz and this give...