Patent ID: 7279941
Filing Date: 2007-10-09
Classification: H03K

Abstract:
1. A voltage-frequency conversion apparatus comprising: a variable current source for charging a capacitor; a current amount adjustment curcuit which has a first resistor for applying a first voltage and a second resistor for applying a second voltage and adjusts the amount of a current from the variable current source to be corresponding to a differential voltage between the first voltage and the second voltage, and a current amount adjustment error amplifier for supplying a current corresponding to the differential voltage between the first voltage and the second voltage to either the first resistor or the second resistor, and to the capacitor; a comparator that compares in level a charging voltage produced at one end of the capacitor and a reference voltage, and generates a frequency signal according to the differential voltage between the first voltage and the second voltage; a discharge circuit that discharges the capacitor according to the comparing result of the comparator when the charging voltage exceeds the reference voltage; and a reference voltage control circuit that, when a resistance of the first resistor or the second resistor varies according to its temperature characteristic, changes the value of the reference voltage according to the variation in the resistance of the first resistor or the second resistor so as to maintain constant a frequency of the frequency signal from the comparator, wherein the reference voltage control circuit comprises: