Voltage-to-frequency converter chips provide a signal frequency output as a function of an analog input voltage. A voltage-to-frequency converter chip is widely used for applications where a temperature proportional output is required in a phase-locked loop. In a voltage to frequency converter circuit, an operational amplifier acts as an input to the voltage-to-frequency converter chip. The input current in the voltage to frequency circuit is directed to a NPN transistor to start its operation. Next, a 1mA current and full scale input voltage is fed to the voltage to frequency converter circuit. This voltage provides bias levels and starts charging current to the capacitor, which in turn generates low non-linear square wave frequency output. There are many types of voltage-to-frequency converter chips. Examples include an AD537 voltage to frequency conversion chip and an AD7740 voltage to frequency conversion chip. AD537 voltage to frequency converter chips are widely used as an accurate reference generator and a precision oscillator system. An AD7740 voltage to frequency converter chip is low cost, ultra-small frequency converter, used for isolation of high common-mode voltages. Other voltage-to-frequency converter chips are commonly available.