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US 6,822,514 B1Granted
Amplifier with miller-effect compensation for use in closed loop system such as low dropout voltage regulator
AssigneeNational Semiconductor Corporation
InventorArlo Aude
Life of this patent
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Abstract
Circuitry including Miller-effect feedback for use as part of a closed loop system such as a low dropout voltage regulator that provides current to a load at a specified voltage close in value to the power supply voltage. Various aspects of the presently claimed invention include using, within the Miller-effect feedback loop: a buffer amplifier to reduce loading effects upon an internal high impedance circuit node, output compensation circuitry to introduce a transfer function pole for substantially canceling a transfer function zero associated with external load circuitry; and Miller-effect compensation circuitry to introduce a transfer function zero for substantially canceling a transfer function pole associated with the Miller-effect feedback.
Claims20
An apparatus including an integrated circuit with a buffer amplifier inside a Miller-effect feedback loop for reducing loading on an internal high impedance circuit terminal, comprising:
- first amplification circuitry including an internal terminal and a first amplifier output terminal, wherein
- said internal terminal has an internal terminal impedance associated therewith,
- said first amplifier output terminal has a first amplifier output terminal impedance associated therewith,
- said internal terminal impedance is substantially lower than said first amplifier output terminal impedance, and
- said first amplification circuitry is adapted to couple via said internal terminal to a Miller-effect feedback capacitance;
- buffer amplification circuitry including buffer input and output terminals, wherein said buffer input terminal is coupled to said first amplifier output terminal;
- and
- second amplification circuitry including a second amplifier input terminal coupled to said buffer output terminal, wherein
- said second amplifier input terminal has a second amplifier input terminal impedance associated therewith,
- said second amplifier input terminal impedance is substantially lower than said first amplifier output terminal impedance, and
- said second amplification circuitry is adapted to couple to further amplification circuitry that includes said Miller-effect feedback capacitance.
8 more elements
An apparatus including an integrated circuit with a buffer amplifier inside a Miller-effect feedback loop for reducing loading on an internal high impedance circuit node, comprising:
- first amplifier means for receiving via an internal node a feedback signal via a Miller-effect feedback capacitance and providing via a first amplifier output node a first amplified signal, wherein
- said internal node has an internal node impedance associated therewith,
- said first amplifier output node has a first amplifier output node impedance associated therewith, and
- said internal node impedance is substantially lower than said first amplifier output node impedance;
- buffer amplifier means for receiving and buffering said first amplified signal and providing a buffered signal;
- and
- second amplifier means for receiving via a second amplifier input node and amplifying said buffered signal and providing a second amplified signal for further amplifier means including said Miller-effect feedback capacitance, wherein
- said second amplifier input node has a second amplifier input node impedance associated therewith, and
- said second amplifier input node impedance is substantially lower than said first amplifier output node impedance.
6 more elements
An apparatus including an integrated circuit with a compensation circuit inside a Miller-effect feedback loop, comprising:
- first amplification circuitry including an internal terminal and a first amplifier output terminal, wherein
- said first amplifier output terminal has a first amplifier output terminal impedance associated therewith, and
- said first amplification circuitry is adapted to couple via said internal terminal to a Miller-effect feedback capacitance;
- second amplification circuitry including a second amplifier input terminal having a second amplifier input terminal impedance associated therewith, wherein
- said second amplifier input terminal impedance is substantially lower than said first amplifier output terminal impedance, and
- said second amplification circuitry is adapted to couple to further amplification circuitry that includes said Miller-effect feedback capacitance and a shunt capacitance having an effective series resistance associated therewith;
- and
- compensation circuitry coupled between said first amplification circuitry and said second amplification circuitry;
- wherein
- said first amplification circuitry, said compensation circuitry and said second amplification circuitry together, when coupled to said further amplification circuitry, have a circuit transfer function associated therewith that includes a transfer function zero associated with at least a portion of said further amplification circuitry and a transfer function pole associated with said compensation circuitry, and
- said transfer function zero and pole are at substantially equal frequencies.
8 more elements
An apparatus including an integrated circuit with a compensation circuit inside a Miller-effect feedback loop, comprising:
- first amplifier means for receiving via an internal node a feedback signal via a Miller-effect feedback capacitance and providing via a first amplifier output node a first amplified signal, wherein said first amplifier output node has a first amplifier output node impedance associated therewith;
- compensation means for compensating said first amplified signal and providing a compensated signal;
- and
- second amplifier means for receiving via a second amplifier input node and amplifying said compensated signal and providing a second amplified signal for further amplifier means including said Miller-effect feedback capacitance and a shunt capacitance having an effective series resistance associated therewith, wherein
- said second amplifier input node has a second amplifier input node impedance associated therewith, and
- said second amplifier input node impedance is substantially lower than said first amplifier output node impedance;
- wherein
- said first amplifier means, said compensation means and said second amplifier means together, when coupled to said further amplifier means, have a transfer function associated therewith that includes a transfer function zero associated with at least a portion of said further amplifier means and a transfer function pole associated with said compensation means, and
- said transfer function zero and pole are at substantially equal frequencies.
6 more elements
An apparatus including an integrated circuit with a plurality of compensation circuits inside a Miller-effect feedback loop, comprising:
- input amplification circuitry including an internal terminal and an input amplifier output terminal, wherein
- said input amplifier output terminal has an input amplifier output terminal impedance associated therewith, and
- said input amplification circuitry is adapted to couple via said internal terminal to a Miller-effect feedback capacitance;
- buffer amplification circuitry including a buffer input terminal coupled to said input amplifier output terminal;
- Miller-effect compensation circuitry coupled between said input amplification circuitry and said buffer amplification circuitry;
- output amplification circuitry including an output amplifier input terminal and adapted to couple to further amplification circuitry that includes said Miller-effect feedback capacitance and a shunt capacitance having an effective series resistance associated therewith;
- and
- output compensation circuitry coupled between said buffer and output amplification circuitry;
- wherein
- said input amplification circuitry, said Miller-effect compensation circuitry, said buffer amplification circuitry, said output compensation circuitry, and said output amplification circuitry together, when coupled to said further amplification circuitry, have a circuit transfer function associated therewith that includes a first transfer function zero associated with said Miller-effect compensation circuitry, a second transfer function zero associated with at least a portion of said further amplification circuitry, a first transfer function pole associated with said Miller-effect feedback capacitance and a second transfer function pole associated with said output compensation circuitry,
- said first transfer function zero and pole are at first substantially equal frequencies, and
- said second transfer function zero and pole are at second substantially equal frequencies.
9 more elements
An apparatus including an integrated circuit with a plurality of compensation circuits inside a Miller-effect feedback loop, comprising:
- input amplifier means for receiving via an internal node a feedback signal via a Miller-effect feedback capacitance and providing via an input amplifier output node a first amplified signal, wherein said input amplifier output node has an input amplifier output node impedance associated therewith;
- Miller-effect compensation means for compensating said first amplified signal and providing a first compensated signal;
- buffer amplifier means for receiving and buffering said first compensated signal and providing a buffered signal;
- output compensation means for compensating said buffered signal and providing a second compensated signal;
- and
- output amplifier means for receiving via an output amplifier input node and amplifying said second compensated signal and providing a second amplified signal for further amplifier means including said Miller-effect feedback capacitance and a shunt capacitance having an effective series resistance associated therewith;
- and
- wherein
- said input amplifier means, said Miller-effect compensation means, said buffer amplifier means, said output compensation means and said output amplifier means together, when coupled to said further amplifier means, have a transfer function associated therewith that includes a first transfer function zero associated with said Miller-effect compensation means, a second transfer function zero associated with at least a portion of said further amplifier means, a first transfer function pole associated with said Miller-effect feedback capacitance and a second transfer function pole associated with said output compensation means,
- said first transfer function zero and pole are at first substantially equal frequencies, and
- said second transfer function zero and pole are at second substantially equal frequencies.
8 more elements
Dependencies are inferred from the claim text.