precision VCO

7-40 elektor july/august 1980 54 According to the author, the lin- earity and synchronisation (when several VCOs are used) of this circuit is very good indeed. When the circuit is correctly set up accuracies of below 0.01% can be achieved! In addition, the voltage controlled oscil- lator presented here is capable of generating square, triangular and sawtooth waveforms as required. This makes it very useful for music synthesiser and measurement appli- cations. Examples of the latter are precision waveform generators and voltage-to-frequency converters. The oscillator consists of a mixer, IC1, and a schmitt-trigger, IC2. When the output of IC2 is positive (+15 V), the FET (T1) will conduct; when the output voltage is negative, however, T1 will be turned off. Thus, T1 operates as an electronic switch. When T1 is conducting, a charge current flows through re- sistors R1 and R2 into the capacitor C1. The voltage at the inverting input of IC1 will be the same as that at the non-invertin...