Patent ID: 8519694

Claim:
A switching circuit for providing a switched current source output, comprising: a reference voltage input device including a transistor having a gate and a drain connected together and connected to a reference current source; a charge storage device for storing a first reference voltage; an output transistor being configured and arranged under control of a gate voltage; an isolating switch for selectively coupling or isolating a gate of the output transistor to or from the charge storage device; a discharge switch for discharging the gate of the output transistor; wherein the switching circuit is operable in both: a precharge mode, in which the reference voltage input device provides the first reference voltage to the charge storage device, the charge storage device is precharged to the first reference voltage, the output transistor gate is discharged through the discharge switch, and the isolating switch isolates the charge storage device from the output transistor gate, and a discharge mode in which the reference voltage input device provides a second reference voltage to the charge storage device, the charge storage device is discharged to the transistor gate through the isolating switch until the voltage input device reaches the second reference voltage; and wherein the control of the gate voltage at the output transistor gate is provided by a controlled charge flow rather than application of a controlled voltage.