precision v-f converter

Although this Voltage Controlled Oscillator uses only two CA3130 op amps the linearity of its voltage/fre- quency transfer characteristic is better than 0.5% and its temperature coef- ficient less than 0.01%/°C. The circuit operates as follows: ICl functions as a voltage controlled multi- vibrator. Assuming that the output volt- age of I Cl is initially + 15 V, Cl will charge via D3, R4 and Pl with a time constant (R4 + Pl) Cl until the voltage on the inverting input of ICl exceeds that on the non-inverting input. Neglecting D1 and D2 for a moment this is approximately 10 V, set by the potential divider Rl, R3 and R2. The output of ICI will now swing down to zero and the voltage on the non- inverting input will fall to about 5 V due to the hysteresis introduced by R3.