High gain rf power amplifier with negative capacitor

Abstract

A radio frequency (RF) power amplifier circuit includes an input and an output. A power amplifier transistor has a first terminal connected to the input, a second terminal connected to the output, and a third terminal defined by a degeneration inductance. A first capacitor is connected to the third terminal of the power amplifier transistor, along with a negative capacitance circuit connected in series with the first capacitor. The negative capacitance and the first capacitor define a series resonance at a predefined operating frequency band, which shunts the degeneration inductance of the third terminal.

What is claimed is: 
     
         1 . A radio frequency (RF) power amplifier circuit for a predefined operating frequency band, the RF power amplifier circuit including an input and an output, comprising:
 a power amplifier transistor with a first terminal connected to the input, a second terminal connected to the output, and a third terminal defined by an inductance;   a first capacitor connected to the third terminal of the power amplifier transistor; and   a negative capacitance circuit connected to the third terminal in series with the first capacitor;   wherein the negative capacitance circuit and the first capacitor define a series resonance at the predefined operating frequency band, the inductance of the third terminal being shunted by the negative capacitance circuit and the first capacitor.   
     
     
         2 . The RF power amplifier circuit of  claim 1 , wherein the negative capacitance circuit and the first capacitor have an equivalent impedance lower than 0.5 Ohm. 
     
     
         3 . The RF power amplifier circuit of  claim 1 , wherein the negative capacitance circuit is connected to ground. 
     
     
         4 . The RF power amplifier circuit of  claim 1 , wherein the negative capacitance circuit includes:
 an operational amplifier with a positive input, a negative input, and an output;   a first negative capacitance circuit capacitor connected to the negative input and the output of the operational amplifier;   a first negative capacitance circuit resistor connected to the positive input and the output of the operational amplifier;   a second negative capacitance circuit resistor connected to the positive input of the operational amplifier.   
     
     
         5 . The RF power amplifier circuit of  claim 4 , wherein the second negative capacitance circuit resistor is connected to ground. 
     
     
         6 . The RF power amplifier circuit of  claim 4 , wherein the negative capacitance circuit includes a negative capacitance circuit inductor connected to the second negative capacitance circuit resistor. 
     
     
         7 . The RF power amplifier circuit of  claim 6 , wherein the negative capacitance circuit inductor is a trace on a semiconductor die. 
     
     
         8 . The RF power amplifier circuit of  claim 1 , wherein the power amplifier transistor, the first capacitor, and the negative capacitance circuit are disposed within an interior region of a semiconductor die. 
     
     
         9 . The RF power amplifier circuit of  claim 1 , wherein the power amplifier transistor is an n-type metal oxide semiconductor transistor, the first terminal being a gate, the second terminal being a drain, and a third terminal being a source, the third terminal being connected to a body of the power amplifier transistor. 
     
     
         10 . The RF power amplifier circuit of  claim 1 , wherein the power amplifier transistor is a bipolar junction transistor, the first terminal being a base, the second terminal being a collector, and the third terminal being an emitter. 
     
     
         11 . The RF power amplifier circuit of  claim 1 , further comprising:
 an input matching circuit connected to the input and the first terminal of the power amplifier transistor; and   an output matching circuit connected to the output and the second terminal of the power amplifier transistor.   
     
     
         12 . The RF power amplifier circuit of  claim 1 , further comprising:
 a control voltage source connected to the first terminal of the power amplifier transistor and defining a bias point thereof.   
     
     
         13 . The RF power amplifier circuit of  claim 1 , further comprising:
 a bias voltage source connected to the second terminal of the power amplifier transistor.