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US 8,493,139 B2Granted
Low noise auto-zero circuits for amplifiers
AssigneeAnalog Devices, Inc.
InventorMark Sayuk
Life of this patent
Estimating the term…
Abstract
An amplifier may include a low noise auto-zero circuit with auto-zero capacitors and switch-controlled auxiliary capacitors that function as switched-capacitor low-pass filters. In an acquisition phase of the auto-zero operation, the inputs of an amplifier may be shorted to a common voltage, and a representation of the offset voltage may be acquired by the auto-zero capacitors. In a hold phase of the auto-zero operation, the auto-zero capacitors may be connected to the auxiliary capacitors, and the resulting voltages may be applied to the circuit such that the original offset voltage is cancelled. Moreover, the switched-capacitor filters may reduce the effective sampling noise while maintaining high acquisition bandwidth.
Claims25
A circuit system, comprising:
- a first transconductance amplifier having a pair of inputs coupled to input terminals of the system and coupled to a common mode voltage source via a first pair of switches,
- a second transconductance amplifier, having a pair of inputs coupled via a second pair of switches to outputs of the first transconductance amplifier and having outputs also coupled to outputs of the first transconductance amplifier,
- a pair of auto-zero capacitors, each coupled to a respective input of the second transconductance amplifier at first terminals thereof and connected to a common voltage at second terminals thereof, and
- a pair of auxiliary capacitors, each provided in parallel with a corresponding auto-zero capacitor via a respective third switch.
1 more element
A circuit system comprising:
- a differential amplifier having a pair of inputs coupled to respective input terminals of the system and coupled to a common mode voltage via respective first switches,
- a pair of auto-zero capacitors, each coupled to a respective output of the differential amplifier at a first terminal thereof and coupled to the common mode voltage via respective second switches,
- a pair of auxiliary capacitors, each coupled to a respective output of the differential amplifier at a first terminal thereof and coupled to a second terminal of a respective auto-zero capacitor via a respective third switch to achieve a current path between the respective auxiliary capacitor and the second terminal of the respective auto-zero capacitor.
A circuit system comprising:
- a differential amplifier having a pair of first switches each coupled between an input and a respective output of the differential amplifier,
- a pair of auto-zero capacitors, each having a first terminal coupled to a respective input of the differential amplifier and a second terminal coupled to a common mode voltage via a respective second switch,
- a pair of auxiliary capacitors, each having:
- (i) a first terminal coupled to a respective input of the differential amplifier and the first terminal of a respective auto-zero capacitor via a respective third switch to achieve a current path between the first terminals of a respective auxiliary capacitor and the respective auto-zero capacitor, and (ii) second terminal coupled to the second terminal of the respective auto-zero capacitor.
1 more element
A circuit system comprising:
- a differential amplifier having a pair of inputs coupled to respective input terminals of the system,
- an auto-zero circuit comprising:
- an auxiliary differential amplifier,
- a pair of auto-zero capacitors, each having a first terminal coupled to a respective input of the auxiliary differential amplifier and a second terminal coupled to a common voltage, and
- a pair of auxiliary capacitors, each having a first terminal coupled to a first terminal of a respective auto-zero capacitor via a switch and a second terminal coupled to the common voltage;
- and
- a pair of subtractors, each having inputs coupled to an output of the differential amplifier and an output of the auxiliary differential amplifier.
4 more elements
A circuit system, comprising:
- a pair of differential amplifiers, each having inputs coupled to a signal source via respective input switches and having outputs coupled to an output terminal via respective output switches, each differential amplifier having a pair of auto-zero capacitors each provided in a signal path between an input and an output of the respective differential amplifier, and a pair of auxiliary capacitors each coupled in parallel with a corresponding auto-zero capacitor via a connecting switch, wherein
- input switches of a first differential amplifier and output switches of a second differential amplifier are closed in a first phase of operation and open in a second phase of operation, and
- input switches of a second differential amplifier and output switches of a first differential amplifier are closed in the second phase of operation and open in the first phase of operation.
A circuit system, comprising:
- means for amplifying a differential signal presented at the circuit system and generating a differential output signal therefrom,
- a pair of auto-zero capacitors, each provided in a signal path between a differential input signal and a differential output signal, and
- a pair of auxiliary capacitors, each provided in parallel with a corresponding auto-zero capacitor via a connecting switch defining parallel current paths between each auxiliary capacitor and its corresponding auto-zero capacitor.
Dependencies are inferred from the claim text.