Patent ID: 8604884

Claim:
An apparatus comprising: an amplifier circuit having a first input coupled to a reference voltage; a first transistor providing a first current that is indicative of a control voltage, a first current carrying terminal of the first transistor coupled to a first power supply node and a second current carrying terminal of the first transistor coupled to a second input of the amplifier circuit and having a gate terminal coupled to an output of the amplifier circuit; a second transistor coupled to supply a mirrored current corresponding to the first current, the second transistor having a gate terminal coupled to a gate terminal of the first transistor and the output of the amplifier circuit, the second transistor having a first current carrying terminal coupled to the first power supply node; an oscillator circuit coupled to a second current carrying terminal of the second transistor and having frequency of oscillation controlled according to the mirrored current, the reference voltage being independent of the second transistor; a third transistor coupled to receive the control voltage at a gate terminal, the third transistor having a first current carrying terminal coupled to the second input of the amplifier circuit and coupled to the second current carrying terminal of the first transistor; and a resistor coupled between a second power supply node and a second current carrying terminal of the third transistor, the resistor used to generate the first current such that it is linearly related to the control voltage, the resistor being coupled to receive the first current.