Voltage controlled oscillator having control current compensation

Abstract

A voltage controlled oscillator (600) includes a voltage to current portion (400) that is inversely proportional to the semiconductor processing in order to compensate for variations both in the low-frequency and high-frequency portions of the VCO gain response. To compensate for low-frequency variations, a portion of the control current (ICTL), non-compensated control current ICTLNC (436), is subtracted from a reference current IREF (408) and the result, a low-frequency compensating control current, ICTLLF (438), is added to the non-compensated control current ICTLNC (436). To compensate for high frequency variations, a number of differential transistor pairs (410-416) are provided that have tail currents that are inversely proportional to the processing. One input (426) to all the differential pairs is connected to the VCO's control voltage while the other inputs (418-424) are connected to successively increasing voltages in the control voltage range. One output, ICTLHF (440), of all the differential pairs is summed with the non-compensated control current ICTLNC (436) while the other output of each differential pair is connected to the power supply. By adjusting the amount of non-compensated control current ICTLNC (436) provided to transistor M1 using the low frequency gain compensation circuit 402 and high frequency gain compensation circuit 404, VCO (400) provides for a process-insensitive, substantially constant gain VCO.

Dependencies are inferred from the claim text.