Patent ID: 9214898
Filing Date: 2015-12-15
Classification: H03F

Abstract:
1. A triple cascode power amplifier, comprising: a first-stage transistor pair comprising two first-stage transistors that respectively receive two dynamic bias voltages with opposite polarities; a second-stage transistor pair coupled with the first-stage transistor pair to four a first node, the second-stage transistor pair comprising two second-stage transistors coupled with each other to form a second node; and a third-stage transistor pair coupled with the second-stage transistor pair, the third-stage transistor pair comprising two third-stage transistors for outputting a differential signal; wherein the first-stage transistor pair and the second-stage transistor pair are low voltage components while the third-stage transistor pair is a high voltage component; and wherein the power amplifier transforms the differential signal into a single-ended signal for output; and a control circuit for generating a control signal at the second node to control a voltage at the first node with respect to a ground within a predetermined range; wherein the control circuit comprises: an operational amplifier, a first input terminal of which receives a first voltage and an output terminal of which generates the control signal; a first current source for supplying a current; a second transistor, a gate of which is coupled with the output terminal of the operational amplifier to form a third node, a drain of which is coupled with the first current source and a source of which is coupled with a second input terminal of the operational amplifier to form a fourth node; and a first transistor, a drain of which is coupled with the fourth node and a source of which is grounded; wherein the second node is coupled to the third node; wherein amplification coefficients of the first transistor and the first-stage transistors are proportional and amplification coefficients of the second transistor and the second-stage transistors are proportional; and wherein a voltage at the first node varies according to a voltage at the fourth node.