US 2004/0104775 A1 · High linearity digital variable gain amplifier

Abstract

Variable gain amplifiers offering high frequency response with improved linearity and reduced power dissipation are provided. An amplifier is disclosed that is constructed from a one-stage topology with multiple signal paths and compensation networks for improved linearity and stable operation. In this amplifier, improved performance is obtained by replacing single transistor components with enhanced active devices which incorporate local negative feedback. One embodiment of the invention is a transconductance enhancement circuit that improves transconductance and input impedance relative to the prior art. A further development is an enhanced active cascode circuit that provides improved linearity. A high frequency bipolar transistor switch is also disclosed that incorporates lateral PNP transistors as high frequency switches with improved OFF-state to ON-state impedance ratio to realize a variable gain function. These circuits are combined in an amplifier circuit that provides variable gain and high frequency performance, with improved linearity, gain, and input impedance.

Claims47

Dependent claims

A composite transistor amplifier with increased linearity that provides an output current to a load, said amplifier comprising:

a first transistor, wherein the base terminal of said first transistor receives an input voltage signal to be amplified and the collector terminal of said first transistor is biased with a first current source;
a second transistor, wherein the base terminal of said second transistor is coupled to the collector terminal of said first transistor, the emitter terminal of said second transistor is coupled to ground, and the collector terminal of said second transistor is biased with a second current source;
a third transistor, wherein the base terminal of said third transistor is coupled to said collector terminal of said second transistor, the emitter terminal of said third transistor is coupled to the emitter terminal of said first transistor, and said output current being derivable from the collector terminal of said third transistor;
and
a feed forward circuit that is coupled between the base terminal of said second transistor and said emitter terminal of said first transistor.

2 more elements

A composite transistor amplifier with increased linearity that provides an output current to a load, said amplifier comprising:

a first transistor, wherein the base terminal of said first transistor receives an input voltage signal to be amplified and the collector terminal of said first transistor is biased with a first current source;
a second transistor, wherein the base terminal of said second transistor is coupled to the collector terminal of said first transistor, the emitter terminal of said second transistor is coupled to ground, and the collector terminal of said second transistor is biased with a second current source;
a third transistor, wherein the base terminal of said third transistor is coupled to said collector terminal of said second transistor, the emitter terminal of said third transistor is coupled to the emitter terminal of said first transistor, and said output current being derivable from the collector terminal of said third transistor;
and
a fourth transistor, wherein the collector terminal of said fourth transistor is coupled to the collector terminal of said first transistor and the emitter terminal of said fourth transistor is coupled to the base terminal of said third transistor, and the base terminal of said fourth transistor is coupled to a first voltage source.

2 more elements

A grounded input active cascode amplifier with increased gain that provides an output current to a load, said amplifier comprising:

a first transistor, wherein the base terminal of said first transistor is coupled to a first supply voltage and the collector terminal of said first transistor is biased with a first current source;
a second transistor, wherein the base terminal of said second transistor is coupled to the collector terminal of said first transistor, the emitter terminal of said second transistor is coupled to an error control input, and the collector terminal of said second transistor is biased with a second current source;
a third transistor, wherein the base terminal of said third transistor is coupled to a second supply voltage and the emitter terminal of said third transistor is coupled to the emitter terminal of said second transistor;
and
a fourth transistor, wherein the base terminal of said fourth transistor is coupled to said collector terminal of said second transistor, the collector terminal of said fourth transistor is coupled to the collector terminal of said third transistor, the emitter terminal of said fourth transistor is coupled to the emitter terminal of said first transistor, said emitter terminal of said fourth transistor that receives an input signal to be amplified, and said output current being derivable from the collector terminal of said fourth transistor;
and
a feed forward circuit that is coupled between the base terminal of said second transistor and the emitter terminal of said first transistor.

4 more elements

A grounded input active cascode amplifier with increased gain that provides an output current to a load, said amplifier comprising:

a first transistor, wherein the base terminal of said first transistor is coupled to a first supply voltage and the collector terminal of said first transistor is biased with a first current source;
a second transistor, wherein the base terminal of said second transistor is coupled to the collector terminal of said first transistor, the emitter terminal of said second transistor is coupled to an error control input, and the collector terminal of said second transistor is biased with a second current source;
a third transistor, wherein the base terminal of said third transistor is coupled to a second supply voltage and the emitter terminal of said third transistor is coupled to the emitter terminal of said second transistor;
and
a fourth transistor, wherein the base terminal of said fourth transistor is coupled to said collector terminal of said second transistor, the collector terminal of said fourth transistor is coupled to the collector terminal of said third transistor, the emitter terminal of said fourth transistor is coupled to the emitter terminal of said first transistor, said emitter terminal of said fourth transistor that receives an input signal to be amplified, and said output current being derivable from the collector terminal of said fourth transistor;
and
a bandwidth limiting circuit that is coupled between said collector terminal of said second transistor and ground.

4 more elements

A one-stage amplifier utilizing multiple amplifiers, the amplifier comprising:

a first bias current source;
a first composite transistor, wherein said composite transistor comprises at least three first component transistors, a first input voltage is provided at the base terminal of said first composite transistor, said first bias current source is coupled to the emitter terminal of said first composite transistor, the collector terminal of said first composite transistor provides an amplified current indicative of said first input voltage;
and
a second composite transistor, wherein said second composite transistor comprises at least three second component transistors, the emitter terminal of said second composite transistor is coupled to the collector terminal of said first composite transistor, the emitter terminal of said second composite transistor is a virtual ground that provides bias voltage to said first composite transistor, the emitter terminal of said second composite transistor is provided bias current by the collector terminal of said first composite transistor.

1 more element

Dependencies are inferred from the claim text.

High linearity digital variable gain amplifier

Life of this patent

High linearity digital variable gain amplifier

Life of this patent

Abstract

Claims47