Patent ID: 8164386

Claim:
An amplifier for providing stable output quiescent current comprising: a plurality of supply rails; an output device configured for providing an output voltage, the output device coupled to the plurality of supply rails, wherein the output device includes: a first n-channel transistor coupled to a low voltage supply rail, and wherein a drain of the first n-channel transistor is configured to provide an output of the amplifier; and a second n-channel transistor, wherein a source of the second n-channel transistor is coupled to a gate of the first n-channel transistor; and an output quiescent current controller coupled to the plurality of supply rails and the output device, the output quiescent current controller matched to the output device to regulate the voltage in the output device to provide a consistent quiescent current in the output device, wherein the output quiescent current controller includes: a third n-channel transistor, wherein a gate of the third n-channel transistor is coupled to a gate of the second n-channel transistor; and a fourth n-channel transistor, wherein a gate of the fourth n-channel transistor is coupled to a source of the third n-channel transistor and a source of the fourth n-channel transistor is coupled to the low voltage supply rail, and wherein during operation a drain to source voltage of the second n-channel transistor is approximately the same as a drain to source voltage of the third n-channel transistor, and wherein the drain to source voltage of the second n-channel transistor and the drain to source voltage of the third n-channel transistor track one another during quiescent operation.