Low power class-AB integrated circuit amplifier
AssigneeCrystal Semiconductor Corporation
InventorShyam S. Somayajula
Life of this patent
Estimating the term…
Abstract
An amplifier circuit having four variable impedance nodes is provided. The amplifier has split transconductance current paths. Each half of the amplifier has two such current paths and each current path has a node which may be either a high impedance or low impedance node. Connected between the two nodes is a transistor which is utilized in driving the nodes to their either high or low impedance state. The invention is particularly useful in a folded cascode amplifier used for driving loud speakers. However, the circuitry may also be used in other amplifiers or other applications.
Claims20
An integrated circuit amplifier circuit, comprising:
- a pair of differential input transistors, said pair including a first input transistor and a second input transistor;
- a first dual transconductance current path connected to said first input transistor, said first dual transconductance current path having at least first and second transconductance current paths;
- a third transistor, a drain of said third transistor connected to said first transconductance current path and a source of said third transistor connected to said second transconductance current path;
- and
- a first output stage driven in class AB mode coupled to said drain and said source.
An integrated circuit amplifier comprising:
- first and second input nodes for receiving a plurality of input voltages;
- a first dual transconductance current path having at least a first and second current branch, current in said first dual transconductance current path indicative of said plurality of input voltages;
- a first voltage node within said first current branch and a second voltage node within said second current branch, each of said first and second voltage nodes capable of being a high impedance state or low impedance state depending upon the operation conditions of said amplifier;
- a transistor having a source connected to said first voltage node and a drain connected to second voltage node, said transistor aiding in driving said first and second output nodes to their respective desired impedance state;
- and
- a first output stage driven in class AB mode coupled to said first voltage node and said second voltage node.
A folded cascode class AB amplifier circuit, comprising:
- first and second input transistors having common sources, a gate of each input transistor connected to an input node of said amplifier;
- a current source connected to a voltage supply, said current source supplying current to said common sources of said input transistors;
- a first split transconductance current path connected to a drain of said first input transistor, said first split transconductance current path having a first and second current branch, said first current branch comprising,
- at least two first current branch transistors having common drains and connected in series between said voltage supply and a drain of said first input transistor, said common drains of said first current branch transistors being a first node,
- said second current branch comprising,
- at least two second current branch transistors having a common drain and connected in series between said voltage supply and said drain of said first input transistor, said common drains of said second current branch transistors being a second node, each of said first and second nodes capable of being a high impedance state or a low impedance state depending upon the operating conditions of said amplifier;
- a transistor having a source connected to said first node and a drain connected to second node, said transistor aiding in driving said first and second output nodes to their respective desired impedance state.
Dependencies are inferred from the claim text.