Electric amplifier circuit for amplifying an output signal of a microphone

Patent metadata

Field	Value
Publication number	US-2016164477-A1
Application number	US-201414904037-A
Country	US
Kind code	A1
Filing date	Jun 27, 2014
Priority date	Jul 10, 2013
Publication date	Jun 9, 2016
Grant date	—

Abstract

An electric amplifier circuit for amplifying an output signal of a microphone comprises a supply input terminal (V 10 ) to apply a supply potential (VDDA) for operating the electric amplifier circuit and a differential amplifier ( 110 ) having a first input terminal (E 110 a ) for applying the output signal of the microphone ( 20 ), a second input terminal (E 110 b ) and an output terminal (A 110 ) for outputting an amplified output signal (OUT) of the microphone ( 20 ). A feedback path (FP) is provided between the output terminal (A 110 ) of the differential amplifier ( 110 ) and the second input terminal (E 110 b ) of the differential amplifier ( 110 ). A charge supplying circuit ( 120 ) is coupled to the feedback path (FP) to supply an amount of the charge to the feedback path (FP) in dependence on the supply potential (VDDA). The amount of charge supplied to the feedback path may be dependent on a change of the supply potential (VDDA).

First claim

1 . An electric amplifier circuit for amplifying an output signal of a microphone, comprising:
a supply input terminal to apply a supply potential for operating the electric amplifier circuit, an input terminal to apply the output signal of the microphone), an output terminal to output an output signal of the amplifier circuit, a differential amplifier having a first input terminal for applying a first input signal, a second input terminal for applying a second input signal and an output terminal for outputting the output signal of the amplifier circuit, wherein the first input terminal of the differential amplifier is coupled to the input terminal of the amplifier circuit, and the output terminal of the differential amplifier is coupled to the output terminal of the amplifier circuit, a feedback path being coupled between the output terminal of the differential amplifier and the second input terminal of the differential amplifier, a charge supplying circuit for supplying a charge, the charge supplying circuit being coupled to the feedback path, wherein the charge supplying circuit is configured to supply an amount of the charge to the feedback path in dependence on a change of the supply potential.

2 . The electric amplifier circuit as claimed in claim 1 ,
wherein the charge supplying circuit is configured to supply an amount of the charge to the feedback path in dependence on the gain of the differential amplifier.

3 . The electric amplifier circuit as claimed in claim 1 ,
wherein said charge supplying circuit comprises an electric storage circuit for storing the charge, wherein the charge supplying circuit is configured such that the amount of charge being stored within the electric storage circuit is dependent on the change of the supply potential and the gain of the differential amplifier.

4 . The electric amplifier circuit as claimed in claim 3 ,
wherein said electric storage circuit comprises at least one capacitor, wherein the at least one capacitor has a first side being connectable with one of the supply potential and a reference potential, and a second side being connected to the feedback path.

5 . The electric amplifier circuit as claimed in claim 4 ,
wherein said electric storage circuit comprises a first capacitor, at least a second capacitor and a controllable switching circuit, wherein said controllable switching circuit is configured to selectively connect the first side of the first capacitor to one of the supply potential and the reference potential, and to selectively connect the first side of the at least one second capacitor to one of the supply potential and the reference potential.

6 . The electric amplifier circuit as claimed in claim 5 ,
wherein the controllable switching circuit comprises a first inverter and at least a second inverter, each of said first and second inverters having a respective terminal to apply the supply potential and a respective terminal to apply the reference potential, wherein the first inverter has an output terminal coupled to the first side of the first capacitor, wherein the first inverter is configured to selectively couple one of the terminals to apply the supply potential and the reference potential to the output terminal of the first inverter in dependence on the gain of the differential amplifier, wherein the at least one second inverter has an output terminal coupled to the first side of the at least one second capacitor, wherein the at least one second inverter is configured to selectively couple one of the terminals to apply the supply potential and the reference potential to the output terminal of the at least one second inverter in dependence on the gain of the differential amplifier.

7 . The electric amplifier circuit as claimed in claim 6 ,
wherein the charge supplying circuit comprises a control circuit having an input side to apply an input signal for the control circuit of the charge supplying circuit, a first output terminal to generate a first control signal, and at least a second output terminal to generate at least a second control signal, said input signal for the control circuit of the charge supplying circuit specifying the gain of the differential amplifier, wherein the first output terminal of the control circuit of the charge supplying circuit is coupled to a control terminal of the first inverter, wherein the first inverter is configured to selectively couple one of the terminals to apply the supply potential and the reference potential to the output terminal of the first inverter in dependence on the first control signal, wherein the at least one second output terminal of the control circuit of the charge supplying circuit is coupled to a control terminal of the at least one second inverter, wherein the at least one second inverter is configured to selectively couple one of the terminals to apply the supply potential and the reference potential to the output terminal of the at least one second inverter in dependence on the second control signaler.

8 . The electric amplifier circuit as claimed in any of claim 1 , comprising:
a transconductance amplifier having a first input terminal to apply a first input signal, a second input terminal to apply a second input signal, and an output terminal to generate an output signal, the output terminal being coupled to the second input terminal of the differential amplifier, wherein the transconductance amplifier is configured to generate an output signal of the transconductance amplifier in dependence on the first and second input signal of the differential amplifier, wherein the charge supplying circuit has an output terminal for supplying the charge, said output terminal being connected to the output terminal of the transconductance amplifier.

9 . The electric amplifier circuit as claimed in claim 8 ,
wherein the first input terminal of the transconductance amplifier is coupled to the output terminal of the amplifier circuit, wherein the second input terminal of the transconductance amplifier is coupled to a voltage source to a apply a reference potential or to the second input terminal of the differential amplifier.

10 . The electric amplifier circuit as claimed in claim 8 , comprising:
a capacitor being connected to the output terminal of the transconductance amplifier and the reference potential, a voltage follower, wherein the voltage follower is arranged in the feedback path between the transconductance amplifier and the second input terminal of the differential amplifier.

11 . The electric amplifier circuit as claimed in claim 10 ,
wherein the first input terminal of the transconductance amplifier coupled to the second input terminal of the differential amplifier, wherein the second input terminal of the transconductance amplifier is coupled to an output terminal of the voltage follower.

12 . The electric amplifier circuit as claimed in claim 1 , comprising:
a first resistor, a second resistor, wherein the first resistor is arranged in the feedback path between an output terminal of the voltage follower and the second input terminal of the differential amplifier, wherein the second resistor is directly connected to the output terminal of the differential amplifier and the second input terminal of the differential amplifier, wherein the differential amplifier is configured such that the gain of the differential amplifier is dependent on the relationship between the first and second resistors.

13 . The electric amplifier circuit as claimed in claim 12 , comprising:
a control circuit to set the gain of the differential amplifier, a storage circuit, wherein the fir

Assignees

• Ams Ag

Inventors

• Duenser Wolfgang
• Bingesser Markus
• Froehlich Thomas

Classifications

• H03F3/183 Primary

  with semiconductor devices only · CPC title

• H03F2200/03

  the amplifier being designed for audio applications · CPC title

• H04R2201/003

  Mems transducers or their use · CPC title

• H03F2203/45116

  Feedback coupled to the input of the differential amplifier · CPC title

• H04R1/04

  Structural association of microphone with electric circuitry therefor (in electric hearing aids H04R25/00) · CPC title