US 7,652,538 B2Granted

Circuits and methods for improving slew rate of differential amplifiers

AssigneeSamsung Electronics Co., Ltd.

InventorYoon-Kyung Choi

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Abstract

Circuits and methods are provided for providing high speed operational amplifiers and, in particular, operational amplifiers having frequency compensation circuits that provide improved slew rates with low power dissipation when configured with feedback. Frequency compensation schemes are provided to enable dynamic configuration of frequency compensation circuits implementing miller compensation whereby nodal connections of compensation capacitors are changed during driver setup and driving periods such that compensation capacitors are connected to source voltages to rapidly charge/discharge compensation capacitors using supply source currents during setup period, while providing frequency compensation during the setup and driving periods to maintain circuit stability and prevent oscillation of an output voltage due to the feedback.

Claims20

Dependent claims

An operational amplifier, comprising:

a first supply voltage rail;
a second supply voltage rail;
a differential amplifier input stage comprising a first signal input terminal and a second signal input terminal;
a folded cascode stage connected to an output of the differential amplifier input stage, the folded cascode stage comprising first, second, third and fourth nodes;
an output driver stage for generating a driving current to an output node of the operational amplifier, the output driver stage comprising first and second output transistors connected to the first and second nodes, respectively, of the folded cascode stage;
and
a compensation circuit connected to the third and fourth nodes of the folded cascode stage and to the output node of the operational amplifier, wherein the output node is connected to the second signal input terminal of the differential amplifier input stage, wherein the compensation circuit comprises:
a first and second capacitor;
and
a first, second, third and fourth switch;
wherein the first switch and the first capacitor are serially connected between the first supply voltage rail and the output node,
wherein the second switch and the second capacitor are serially connected between the second supply voltage rail and the output node;
wherein the third switch is connected to the third node of the folded cascode stage and to a node between the first switch and the first capacitor;
and
wherein the fourth switch is connected to the fourth node of the folded cascode stage and to a node between the second switch and the second capacitor.

12 more elements

An operational amplifier, comprising:

a first differential amplifier input stage having an output node N1;
a second stage having an input node and an output node, wherein the input node of the second stage is coupled to the output node N1 and wherein the output node of the second is an output node NOUT of the operational amplifier, wherein the second stage drives an output voltage on the output node NOUT;
and
a frequency compensation circuit connected between the output node NOUT and the output node N1 of the first differential amplifier input stage;
wherein the frequency compensation circuit comprises:
a first capacitor;
and
a first and second switch;
wherein the first switch and the first capacitor are serially connected between a supply voltage rail and the output node NOUT;
and
wherein the second switch is connected to the output node N1 and to a node between the first switch and the first capacitor such that the second switch and first capacitor are serially connected between the output nodes N1 and NOUT and serially connected in parallel to the second stage.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/228,998Filed 16 Sep 2005
Priority: KR 10-2004-007715624 Sep 2004
Published: US 2006/0091955 A14 May 2006
Granted: 26 Jan 2010
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

H03F 1/34
Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements:…
H03F 1/08
Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements: modifications of…
H03F 3/3022
With field-effect transistors: cMOS common source output SEPP amplifiers
H03F 3/45192
Long tailed pairs: folded cascode stages