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US 7,679,445 B2Granted
Independent dominant pole compensation of two loops using one compensating element
AssigneeAnalog Devices, Inc.
InventorsKenneth A. Lawas, Kimo Y. F. Tam
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Abstract
Disclosed is a differential amplifier system that maintains high speed characteristics of the differential amplifier while providing stability from a common-mode loop by using dominant pole compensation. The disclosed system includes a first and second transconductance stage, a circuit having high impedance, and a compensation circuit.
Claims23
A differential amplifier system, comprising:
- a pair of high impedance current paths including system outputs;
- a first transconductance stage having an input, having outputs connected to respective first nodes of each of the pair of high impedance current paths, and having inputs for differential voltage signals from respective second nodes of each of the high impedance current paths;
- a second transconductance stage having inputs for an approximate average of the system outputs and for a reference voltage and having an output for a current generated therefrom, the generated current input into each of the high impedance current paths;
- and
- a compensation circuit comprising capacitive elements connected to the pair of high impedance current paths and connected to the output of the second transconductance stage the capacitive elements having a value.
2 more elements
A differential amplifier system, comprising:
- a pair of high impedance current paths;
- a first transconductance stage comprising:
- a first transconductance amplifier having inputs for differential voltage signals and having outputs for a pair of differential current signals generated from the inputs, the outputs connected to respective first nodes of each of the high impedance current paths, and
- inputs connected to the high impedance current paths for feeding back differential voltage signals form each of the pair of high impedance currents paths;
- a second transconductance stage having inputs for an average of the differential amplifier system outputs and for a reference voltage and having an output for a current generated therefrom, the generated current input into each of the high impedance current paths;
- and
- a compensation circuit comprising capacitive elements connected to the differential amplifier system output terminals and connected to ground, the capacitive elements having a value.
4 more elements
A method of compensating a differential amplifier system, comprising:
- inputting first differential voltage signals into a first transconductance amplifier of a first transconductance stage;
- outputting from the first transconductance amplifier a pair of differential current signals to respective first nodes of a pair of high impedance current paths;
- inputting second differential voltage signals into a second transconductance amplifier of the first transconductance stage connected to respective second nodes of each of the pair of high impedance current paths;
- outputting a second pair of differential current signals to respective outputs of the first transconductance amplifier, wherein inputs of the second transconductance amplifier are system outputs for the differential amplifier system;
- averaging the system outputs for input into a second transconductance stage;
- comparing, at the second transconductance stage, the average system outputs to a reference voltage;
- generating a current by the second transconductance stage based on the difference of the system average from the reference voltage;
- outputting the generated current into each of the high impedance current paths;
- and
- compensating the differential amplifier system by connecting capacitive elements to the system output terminals and to the output of the second transconductance stage.
7 more elements
A differential amplifier system, comprising:
- a pair of high impedance current paths including system outputs;
- a first transconductance stage having inputs and outputs connected to each of the high impedance current paths, comprising:
- a first transconductance amplifier having inputs for differential voltage signals and having outputs for a pair of differential current signals generated from the inputs, the outputs connected to respective first nodes of each of the high impedance current paths, a second transconductance amplifier having inputs for differential voltage signals connected to respective second nodes of the each of the high impedance current paths and having outputs for a pair of differential current signals connected to respective outputs of the first transconductance amplifier, wherein inputs of the second transconductance amplifier are outputs for the differential amplifier system;
- a second transconductance stage having inputs for an average of the system outputs and for a reference voltage and having an output for a current generated therefrom, the generated current input into each of the high impedance current paths;
- and
- a compensation circuit comprising capacitive elements connected to the pair of high impedance current paths and connected to the output of the second transconductance stage, the capacitive elements having a value.
3 more elements
Dependencies are inferred from the claim text.