Single-end-to-differential microphone circuit

Patent metadata

Field	Value
Publication number	US-12289082-B2
Application number	US-202217918894-A
Country	US
Kind code	B2
Filing date	May 19, 2022
Priority date	Apr 19, 2022
Publication date	Apr 29, 2025
Grant date	Apr 29, 2025

Abstract

The present invention provides a single-end-to-differential microphone circuit, including a power supply end for inputting a first bias voltage, a microphone capacitor, a coupling capacitor, a first primary amplifier, a second primary amplifier, a signal processing module, current sharing amplifier, a feedback resistor at positive end, a feedback capacitor at positive end, a feedback resistor at negative end, a feedback capacitor at negative end. Compared with the prior art, the single-end-to-differential microphone circuit of the present invention can utilize the current sharing amplifier with a small input common mode voltage range and low noise to realize the single-end-to-differential of the signal, which is beneficial to improve the signal to noise ratio of the circuit.

First claim

What is claimed is:

1. A single-end-to-differential microphone circuit, including:
a power supply end for inputting a first bias voltage;
a microphone capacitor;
a coupling capacitor;
a first primary amplifier;
a second primary amplifier;
a signal processing module;
a current sharing amplifier;
a feedback resistor at a positive end;
a feedback capacitor at the positive end;
a feedback resistor at a negative end;
a feedback capacitor at the negative end; wherein
the microphone capacitor is equivalently formed when the microphone is connected to the single-end-to-differential microphone circuit;
the power supply end is connected to a bias voltage input end of the microphone capacitor, and an output end of the microphone capacitor is connected to the first primary input end of the amplifier;
the coupling capacitor is grounded or connected to the bias voltage input end; and wherein
the positive electrode of the coupling capacitor is connected to the bias voltage input end, the single-end-to-differential microphone circuit further includes a first bias resistor connected in series between the power supply end and the bias voltage input end; the coupling capacitor is connected to the second primary input end of the amplifier;
the first primary output end of the amplifier and the second primary output end of the amplifier are respectively connected to the positive input end and the negative input end of the signal processing module; the positive output end and the negative output end of the signal processing module are respectively connected to the positive input end and the negative input end of the current sharing amplifier; the signal processing module adjusts the output signals of the first primary amplifier and the second primary amplifier to a target differential signal with equal vibration amplitude and adverse phase, and outputs the target differential signal to the current sharing amplifier;
the feedback resistor at the positive end and the feedback capacitor at the positive end are connected in parallel between the positive input end and the negative output end of the current sharing amplifier; the feedback resistor at negative end and the feedback capacitor at negative end are connected in parallel between the negative input end and the positive output end of the current sharing amplifier.

2. The single-end-to-differential microphone circuit as described in claim 1 , wherein the signal processing module includes a signal multiplier, and the signal multiplier is used for subtracting the output signal of the second primary amplifier from the output signal of the first primary amplifier to obtain the difference signal; the inversion processing on the difference signal is performed to obtain a difference inversion signal, and the difference signal and the difference inversion signal constitute the target differential signal; the difference signal is output from the positive output end of the signal processing module, and the difference inversion signal is output from the negative output end of the signal processing module.

3. The single-end-to-differential microphone circuit as described in claim 2 , wherein
the signal multiplier includes four switch capacitors; each of the switch capacitors includes two first switches, two second switches and a capacitor; the four switch capacitors are respectively the first switch capacitor, the second switch capacitor, the third switch capacitor and the fourth switch capacitor;
the positive electrode of the capacitor of the first switch capacitor is connected to the positive input end of the signal processing module through one of the first switches connected to the positive output end of the signal processing module through a second switch;
the negative terminal of the capacitor is connected to the negative input end of the signal processing module through the other first switch, and connected to input common mode voltage through the other second switch;
the positive pole of the capacitor of the second switch capacitor is connected to the positive input end of the signal processing module through one of the first switch, and is connected to the input common mode voltage through one of the second switch, the negative terminal of the capacitor is connected to the negative input end of the signal processing module through the other first switch, connected to the negative output end of the signal processing module through the other second switch;
the positive pole of the capacitor of the third switch capacitor is connected to the positive output end of the signal processing module through the first switch, and connected to the positive input end of the signal processing module through a second switch; the negative pole of the capacitor is connected to the input common mode voltage through the other first switch, and connected to the negative input end of the signal processing module through the other second switch;
the positive electrode of the capacitor of the fourth switch capacitor is connected to the input common mode voltage through the first switch, and is connected to the positive input end of the signal processing module through the second switch;
the capacitor is connected to the negative output end of the signal processing module through the other first switch, and is connected to the negative input end of the signal processing module through the other second switch;
all the first switch and the second switch are controlled by the set clock signal: when the clock signal is in the first phase, all the first switches are closed, and all the second switches are open; when the clock signal is the second phase adverse to the first phase, all the first switches are closed, and all the second switches are open.

4. The single-end-to-differential microphone circuit as described in claim 1 , wherein
the single-end-to-differential microphone circuit further includes a first chopper switch and a second chopper switch;
the first chopper switch is connected in series between the output end of the microphone and the first primary input end of the amplifier through an input end and an output end; the first chopper switch is connected in series between the negative pole of the coupling capacitor and the second primary input end of the amplifier, through the other input end and the other output end;
the second chopper switch is connected in series between the first primary output end of the amplifier and the positive input end of the signal processing module through an input end and an output end; the second chopper switch is connected in series between the second initial output end of the amplifier and the negative input end of the signal processing module, through the other input end and the other output end.

5. The single-end-to-differential microphone circuit as described in claim 1 , wherein the current sharing amplifier includes a bias current source, a first PMOS tube, a second PMOS tube, a first NMOS tube, a second NMOS tube, a third NMOS tube and a fourth NMOS tube;
the source electrode of the first PMOS tube and the source electrode of the second PMOS tube are connected to the output end of the bias current source; the grid electrode of the first PMOS tube is connected to grid electrode of the first NMOS tube and together serve as the positive input end of the current sharing amplifier; the drain electrode of the first PMOS tube is connected to the drain electrode of the first NMOS tube and the grid electrode of the third NMOS tube and together serve as the negative output end of the current sharing amplifier;
the grid electrode of the second PMOS tube is connected to the grid electrode of the second NMOS tube and together serve as the negative input end of the current sharing amplifier; the drain electrode of the second PMOS tube is connected to the drain

Assignees

• Aac Acoustic Tech Shenzhen Co Ltd

Inventors

• Han Dong
• Kee Chuationg

Classifications

• H04R2201/003

  Mems transducers or their use · CPC title

• H04R19/04 Primary

  Microphones (H04R19/01 takes precedence) · CPC title

• H04R3/00

  Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) · CPC title

• H03F2200/03

  the amplifier being designed for audio applications · CPC title

• H03F3/45237

  Complementary long tailed pairs having parallel inputs and being supplied in series · CPC title