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Pre-Amplifier for MEMS Microphone
- Rajkumar Sharma
- 508 Views
- easy
- Tested
- SKU: EL116919
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This is a low-cost, small-size audio pre-amplifier for MEMS microphone, OPAMP-based circuit amplifies the low-level analog signal coming from MEMS microphone to the desired level required for the next stage which is an audio amplifier, basically microphone level to line level.
Resistor R4 and R7 are used to generate a voltage reference to bias the input common-mode voltage of the op-amp at VCC/2, C7, C8, and R7 help to reduce power supply noise. R5 and C5 allow AC coupling of the microphone signal. R2 and C2 create a low-pass gain so as not to amplify noise beyond the audio bandwidth. R3 and C6 create a high-pass gain so as not to amplify the DC biasing of the op-amp (including input offset voltage). The cut-off frequency is 59 Hz. D1 is a power LED, this board has a dual option for MEMS microphones. Users may solder onboard microphones or connect external microphones. This board is tested with external Analog MEMS microphone modules from PUI Audio which comes with 3 connections VCC, GND, and output.
Features
- Supply 3.3V
- Very Low Noise Output
- On-Board Power LED
- Dual Microphone Option (Onboard or External Microphone)
- The OPAMP gain is set to 32 (Gain = 1+R2/R3)
- PCB Dimensions 27.78 x 14.29 mm
Schematic
Parts List
| NO. | QNTY. | REF. | DESC. | MANUFACTURER | SUPPLIER | PART NO |
|---|---|---|---|---|---|---|
| 1 | 1 | CN1 | 4 PIN MALE HEADER CONNECTOR PITCH 2.54MM | WURTH | DIGIKEY | 732-5317-ND |
| 2 | 1 | CN2 | AMM-3742-T-EB-R | PUI AUDIO | DIGIKEY | 668-AMM-3742-T-EB-R-ND |
| 3 | 2 | C1,C5 | 1uF/25V SMD SIZE 1206 | MURATA/YAGEO | DIGIKEY | |
| 4 | 1 | C2 | 560PF/50V SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 5 | 1 | C3 | 0.1uF/50V SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 6 | 2 | C4,C8 | 10uF/6.3V SMD SIZE 1206 | MURATA/YAGEO | DIGIKEY | |
| 7 | 1 | C6 | 3.3uF/10V SMD SIZE 1206 | MURATA/YAGEO | DIGIKEY | |
| 8 | 1 | C7 | 22uF/10V SMD SIZE 1206 | MURATA/YAGEO | DIGIKEY | |
| 9 | 1 | D1 | LED SMD SIZE 0805 | LITE ON INC | DIGIKEY | 160-1427-1-ND |
| 10 | 1 | R1 | 1K 5% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 11 | 1 | R2 | 27K 5% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 12 | 1 | R3 | 820E 5% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 13 | 4 | R4,R5,R6,R7 | 10K 5% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 14 | 1 | U1 | TS971 | ST | DIGIKEY | 497-8150-1-ND |
| 15 | 1 | U2 | ICS-40180( Optional) DO NOT POPULATE | TDK |
Connections
MEMS Microphone Specifications
Gerber View
Photos
Video
ICS-40180 Datasheet
PCB
