Thick oxide P-gate NMOS capacitor for use in a phase-locked loop circuit and method of making same

摘要

In a low-pass filter for a phase locked loop (PLL) circuit, a capacitor formed by an N-type substrate, a P-type region formed on the N-type substrate, a thick oxide formed over the P-type region, a P+ gate electrode formed over the thick oxide and coupled to a first voltage supply line, and P+ pick-up terminals formed in the P-type region adjacent the gate electrode and coupled to a second voltage supply line, whereby a gate-to-substrate voltage is maintained at less than zero volts to maintain a stable control voltage for the PLL.