A delay circuit is described having a variable capacitor and a triggering
circuit. The variable capacitor and the triggering circuit may both
comprise transistors. With both the variable capacitor and the triggering
circuit dependent on the threshold voltage, the delay circuit may be less
sensitive to process variations. The delay circuit may also include a
capacitor, a first triggering circuit, a second triggering circuit, and a
pull down circuit. The capacitor may discharge at a first rate,
triggering the first triggering circuit which, in turn, activates the
pull down circuit to pull down the capacitor at a second rate that is
faster than the first rate. The second triggering circuit is triggered as
the capacitor is pulled down, thereby reducing the effect of input signal
noise on the output of the delay circuit. The discharging of the
capacitor may be adjusted by a control input thereby making the delay of
the delay circuit programmable.