VOLTAGE/FREQUENCY CONVERSION CIRCUIT

摘要

PURPOSE:To suppress fluctuation in the output frequency caused by temperature fluctuation. CONSTITUTION:An integration circuit 11 comprises an operational amplifier 111 having an inverted input terminal and an output terminal connected through a capacitor 115. A comparator circuit 12 comprises a comparator 121 having open collector output for reversing the ramp of an integrated output V2 by switching charge/discharge of the capacitor 115 using a comparison output V3. A comparator circuit 13 comprises a comparator 131 having open collector output for comparing the integrated output V2 with a threshold voltage Vth through a predetermined hysteresis. An output Vo from the comparator circuit 13 is fed to the comparator circuit 12 and a voltage signal V1 is fed to the integration circuit 11. The comparator circuit 13 produces a frequency signal Fo. A capacitor 136 imparts a ramp to the rising of an output Vo from the comparison circuit 13 and a circuit 14 alters the reference voltage Vref of the comparator circuit 12 as the temperature rises.