Abstract: A voltage controlled oscillator has a linear voltage to current characteristic from ground to the supply voltage. This oscillator includes a voltage to current converter which employs two output current paths. The first output current path includes an N-type MOSFET whose gate receives the input voltage. A level shifter circuit receives the input voltage and provides an output voltage shifted up by an amount equal to the input threshold voltage of an N-type MOSFET. A clamp circuit connected to the output of the level shifter circuit prevents this output voltage from becoming greater than a voltage equal to the sum of the input threshold voltage of an N-type MOSFET and the input threshold voltage of a P-type MOSFET. The gate of the second N-type MOSFET receives the output of the level shifter as clamped by the clamp circuit. A current mirror circuit supplies a current control to ring oscillator, whose frequency depends upon the current. A second embodiment includes a new ring oscillator.