Amplifier with gain stages coupled for differential error correction
First Claim
1. An amplifier circuit comprisinga first inverting amplifier stage having a first input terminal, a first coupling terminal and a first output terminal, said first inverting amplifier stage also having a first input resistor connected to said first input terminal and a first feedback resistor connected between said first output terminal and said first input terminal,a second inverting amplifier stage having a second input terminal, a second coupling terminal and a second output terminal, said second inverting amplifier stage also having a second input resistor connected to said second input terminal and a second feedback resistor connected between said second output terminal and said second input terminal, said first and second inverting amplifier stages being identical, andmeans for coupling said first and second coupling terminals together, each of said first and second coupling terminals acting simultaneously as a positive input terminal of its corresponding amplifier stage, a complementary output of the corresponding amplifier stage for negative signal coupling to the other amplifier stage, and means for positively communicating distortion and noise contributions of the corresponding amplifier stage to the other amplifier stage, such that differential input signals received by said first and second input terminals are amplified and provided as balanced differential output signals on said first and second output terminals and such that distortion and noise contributions of both amplifier stages are provided in common on said first and second output terminals.
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Accused Products
Abstract
An amplifier circuit having two identical inverting folded-cascode amplifier stages coupled together through a coupling resistor at the positive terminals of the respective stages. Each stage includes an input gain transistor whose gate forms the negative input terminal of the amplifier stage coupled to receive an input signal through an input resistor, whose source forms the positive input terminal of the amplifier stage, and whose drain is connected to the source of a level-shifting cascode transistor. Both transistors are supplied current from a constant current source also connected to the source of the level-shifting transistor. The drain of the level-shifting transistor forms an output terminal of the amplifier stage. Each stage feeds its amplifier output negatively to the positive input of the other stage, while at the same time feeding its distortion and noise contribution positively, via input gain transistor conduction, to the other stage. Balanced amplified outputs are produced from either balanced or unbalanced inputs, and distortion and noise components are produced in common on both outputs for differential cancellation. Complementary-symmetry and power amplifier versions of the basic single-ended line-level amplifier are also provided.
26 Citations
13 Claims
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1. An amplifier circuit comprising
a first inverting amplifier stage having a first input terminal, a first coupling terminal and a first output terminal, said first inverting amplifier stage also having a first input resistor connected to said first input terminal and a first feedback resistor connected between said first output terminal and said first input terminal, a second inverting amplifier stage having a second input terminal, a second coupling terminal and a second output terminal, said second inverting amplifier stage also having a second input resistor connected to said second input terminal and a second feedback resistor connected between said second output terminal and said second input terminal, said first and second inverting amplifier stages being identical, and means for coupling said first and second coupling terminals together, each of said first and second coupling terminals acting simultaneously as a positive input terminal of its corresponding amplifier stage, a complementary output of the corresponding amplifier stage for negative signal coupling to the other amplifier stage, and means for positively communicating distortion and noise contributions of the corresponding amplifier stage to the other amplifier stage, such that differential input signals received by said first and second input terminals are amplified and provided as balanced differential output signals on said first and second output terminals and such that distortion and noise contributions of both amplifier stages are provided in common on said first and second output terminals.
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6. An amplifier circuit comprising
a first inverting folded-cascode amplifier having a first input gain transistor with a source, a drain and a gate connected to a first input resistor, a first cascode level-shifting transistor with a source connected to the drain of said first input gain transistor, a drain coupled to a first output terminal, and a gate connected to a bias voltage selected to maintain said first cascode level-shifting transistor in a conducting state, a first feedback resistor connected between said first output terminal and said gate of said first input gain transistor, and a first constant current source connected to said drain of said first input gain transistor and said source of said first cascode level-shifting transistor, said first constant current source coupled to a first power supply, said source of said first input gain transistor and said drain of said first cascode level-shifting transistor coupled to a second power supply, said first and second power supplies being of balanced voltages, a second inverting folded-cascode amplifier having a second input gain transistor with a source, a drain and a gate connected to a second input resistor, a second cascode level-shifting transistor with a source connected to the drain of said second input gain transistor, a drain coupled to a second output terminal, and a gate connected to a bias voltage selected to maintain said second cascode level-shifting transistor in a conducting state, a second feedback resistor connected between said second output terminal and said gate of said second input gain transistor, and a second constant current source connected to said drain of said second input gain transistor and said source of said second cascode level-shifting transistor, said second constant current source coupled to said first power supply, said source of said second input gain transistor and said drain of said second cascode level-shifting transistor coupled to said second power supply, said second inverting folded-cascode amplifier having substantially the same operating characteristics as said first inverting folded-cascode amplifier, and means, connected between said sources of said first and second input gain transistors, for coupling said first inverting folded-cascode amplifier to said second inverting folded-cascode amplifier.
Specification