Patent ID: 6930555

Claim:
An electrical circuit comprising: an amplifying transistor comprising a base terminal coupled to an input node; and a power control circuit, wherein the power control circuit comprises: a sense transistor comprising a base terminal and a collector terminal, wherein the base terminal is coupled to the base terminal of the amplifying transistor, the collector terminal is coupled to a ground via a capacitor, and the collector terminal is coupled to a reference voltage source via a first resistor; an error amplifier comprising a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal is coupled to the collector of the sense transistor, the first input terminal is coupled to a control voltage source via a second resistor, and the output terminal of the first error amplifier is coupled to the input node; and a third resistor and a fourth resistor coupled in series between the reference voltage source and the ground, wherein the second input of the error amplifier is coupled to a node between the third and the fourth resistors, and wherein the ratio of the resistance of the first resistor to a resistance of the second resistor is about equal to the ratio of the resistance of the third resistor to a resistance of the fourth resistor.