Amplifying electronic circuit with reduced start-up time for a signal including quadrature components

Patent metadata

Field	Value
Publication number	US-10177720-B2
Application number	US-201615156172-A
Country	US
Kind code	B2
Filing date	May 16, 2016
Priority date	Dec 23, 2015
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

An electronic circuit for amplifying signals with two components in phase quadrature, which includes: a feedback amplifier with a feedback capacitor; a switch that drives charging and discharging of the feedback capacitor; an additional capacitor; and a coupling circuit, which alternatively connects the additional capacitor in parallel to the feedback capacitor or else decouples the additional capacitor from the feedback capacitor. The switch opens at a first instant, where a first one of the two components assumes a first zero value; the coupling circuit decouples the additional capacitor from the feedback capacitor in a way synchronous with a second instant, where the first component assumes a second zero value.

First claim

The invention claimed is:

1. An electronic circuit, comprising:
an amplifier including a first input terminal and a first output terminal, the first input terminal being configured to receive an input signal having first and second input components, the first and second input components having a same period and being in phase quadrature with respect to one another;
a first feedback capacitor coupled between the first input terminal and the first output terminal of the amplifier;
a first switch coupled between the first input terminal and the first output terminal of the amplifier;
a first resistor coupled between the first input terminal and the first output terminal of the amplifier; and
a first coupling circuit including a second switch, a third switch and a first startup capacitor, the second switch being coupled between the first input terminal of the amplifier and a first terminal of the first startup capacitor, the third switch being coupled between a second terminal of the first startup capacitor and the first output terminal of the amplifier.

2. The electronic circuit according to claim 1 , said electronic circuit being configured to amplify said input signal as a function of a value of capacitance present between the first input terminal and the first output terminal of the amplifier.

3. The electronic circuit according to claim 1 , the first coupling circuit being configured to selectively operate in a first and a second operating mode, wherein in the first operating mode the second and third switches are configured to couple the first startup capacitor in parallel to the first feedback capacitor, and in the second operating mode the second and third switches are configured to decouple the first startup capacitor from the first feedback capacitor.

4. The electronic circuit according to claim 3 , wherein said first switch is configured to switch from a closed state to an open state in synchronization with a first zero crossing of one of the first and second input components, and wherein the first coupling circuit is configured to switch from the first operating mode to the second operating mode in synchronization with a second zero crossing of said one of the first and second input components.

5. The electronic circuit according to claim 1 , wherein the first feedback capacitor and the first startup capacitor have a substantially same capacitance.

6. The electronic circuit according to claim 3 , the amplifier further including a second input terminal and a second output terminal, the second input terminal being configured to receive the input signal, the electronic circuit further comprising: a second feedback capacitor coupled between the second input terminal and the second output terminal of the amplifier, the second feedback capacitor having a substantially same capacitance as the first feedback capacitor;
a fourth switch coupled between the second input terminal and the second output terminal of the amplifier; and
a second coupling circuit including a fifth switch, a sixth switch and a second startup capacitor, the fifth switch being coupled between the second input terminal of the amplifier and a first terminal of the second startup capacitor, the sixth switch being coupled between a second terminal of the second startup capacitor and the second output terminal of the amplifier, the second startup capacitor having a substantially same capacitance as the first startup capacitor,
wherein the second coupling circuit is configured to selectively operate in synchronization with the first coupling circuit in the first and second operating modes, wherein in the first operating mode, the fifth and sixth switches are configured to couple the second startup capacitor in parallel to the second feedback capacitor, and in the second operating mode the fifth and sixth switches are configured to decouple the second startup capacitor from the second feedback capacitor,
wherein the fourth switch is configured to operate in synchronization with the first switch.

7. The electronic circuit according to claim 3 , wherein said first switch is configured to switch from a closed state to an open state in synchronization with a first zero crossing of one of the first and second input components, and the first coupling circuit is configured to operate in the second operating mode at said first zero crossing and to switch into the first operating mode for a time interval spanning a second zero crossing of said one of the first and second input components.

8. The electronic circuit according to claim 7 , wherein said second said time interval is centered around and symmetrical with respect to said second zero crossing.

9. The electronic circuit according to claim 7 , wherein said time interval has a temporal duration of less than 1/50 of said period.

10. The electronic circuit according to claim 7 , wherein, in the second operating mode, the second and third switches of the first coupling circuit are configured to couple the first and second terminals of the first startup capacitor to a reference potential.

11. The electronic circuit according to claim 6 , further comprising:
a second resistor coupled between the second input terminal and the second output terminal of the amplifier.

12. The electronic circuit according to claim 1 , further comprising:
a synchronization circuit configured to receive an electrical reference signal in phase with one of said first and second input components, and to generate a first control signal for controlling said first switch and a second control signal for controlling said second and third switches of said first coupling circuit.

13. An electronic system comprising:
a gyroscope including first and second input capacitors; and
an electronic circuit coupled to the gyroscope, the electronic circuit including:
an amplifier including a first input terminal and a first output terminal, the first input terminal being configured to receive an input signal having first and second input components, the first and second input components having a same period and being in phase quadrature with respect to one another;
a first feedback capacitor coupled between the first input terminal and the first output terminal of the amplifier;
a first resistor coupled between the first input terminal and the first output terminal of the amplifier;
a first switch coupled between the first input terminal and the first output terminal of the amplifier; and
a first coupling circuit including a second switch, a third switch and a first startup capacitor, the second switch being coupled between the first input terminal of the amplifier and a first terminal of the first startup capacitor, the third switch being coupled between a second terminal of the first startup capacitor and the first output terminal of the amplifier.

14. The electronic system of claim 13 wherein the electronic circuit further includes:
a second feedback capacitor coupled between the second input terminal and the second output terminal of the amplifier;
a fourth switch coupled between the second input terminal and the second output terminal of the amplifier; and
a second coupling circuit including a fifth switch, a sixth switch and a second startup capacitor, the fifth switch being coupled between the second input terminal of the amplifier and a first terminal of the second startup capacitor, the sixth switch being coupled between a second terminal of the second startup capacitor and the second output terminal of the amplifier.

15. The electronic system according to claim 14 , the electronic circuit being configured to selectively operat

Assignees

• St Microelectronics Srl

Inventors

• Nicollini Germano
• Garbarino Marco

Classifications

• H03F2200/336

  A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit · CPC title

• H03F2203/45536

  the FBC comprising a switch and being coupled between the LC and the IC · CPC title

• H03F1/3211 Primary

  in differential amplifiers · CPC title

• H03K5/1536

  Zero-crossing detectors (in measuring circuits G01R19/175) · CPC title

• H03F1/34 Primary

  Negative-feedback-circuit arrangements with or without positive feedback (H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence {; for rejection of common mode signals H03F3/45479}) · CPC title