A signal processing circuit is provided, such as a PIN diode attenuator for use in cable television signal distribution. The circuit includes a variable impedance device that is responsive to an input signal. The input signal is provided over a first range to vary the impedance in response to a control signal having an absolute value below a predetermined threshold. The input signal is provided over a second range in response to the control signal having an absolute value above the threshold. The first and second ranges are not contiguous. In a preferred embodiment, a zener diode is used to increase the drive current to a bridged-T PIN diode attenuator when the attenuator control signal reaches the zener breakdown voltage.