Power amplifier with a bootstrapped driver stage

Abstract

A power amplifier includes a bootstrapped driver circuit in which the load element is divided into two parts. A single-ended push-pull circuit provides a feedback to the junction point of those two parts. A resistor element having 0.1 to 10 times the resistance of the load element is connected in parallel with the load element.

What is claimed is: 
     
       1. A power amplifier comprising: a driver circuit comprising an input terminal, an output terminal, signal amplifying means and a load element formed by two separate resistors, a first end of the first resistor being connected to said signal amplifying means and a second end of said first resistor being connected to said second resistor;   an output circuit comprising at least one input terminal connected directly to the output terminal of said driver circuit, output transistors connected in a single-ended push-pull configuration, and an output terminal;   feedback means for supplying a feedback signal from the output terminal of said output circuit to said second end of said first resistor; and   a third resistor connected directly to and in parallel with said load element.   
     
     
       2. The power amplifier of claim 1, wherein the resistance value of said third resistor is approximately within the range of 0.1 to 10 times that of said load element of said driver circuit. 
     
     
       3. The power amplifier of claim 1, further comprising: a pre-amplifier circuit comprising an input terminal, an output terminal connected to said input terminal of said driver circuit, and a feedback terminal; and   an additional feedback means connected between said output terminal of said output circuit and said feedback terminal of said pre-amplifier circuit for supplying a part of the output signal of said output circuit to said feedback terminal in inverse phase relationship.