Microphone Amplifier Module with AGC and Low-Noise Bias – MAX9814 User’s Guide
MAX9814 Microphone Amplifier Module (No SHDN Pin) – User’s Guide
Overview
This variant of the MAX9814 module retains core features:
- Automatic Gain Control (AGC) for dynamic sound environments
- Low-noise microphone bias
- Selectable gain levels (typically 40dB, 50dB, 60dB)
- Simplified pinout for easier integration
Ideal for voice detection, sound-reactive lighting, audio logging, and embedded sound triggers.
Technical Specifications
| Parameter | Value |
|---|---|
| Supply Voltage | 2.7V – 5.5V |
| Current Consumption | ~3mA |
| Output Signal | ~2Vpp centered around 1.25V DC |
| Frequency Response | 20Hz – 20kHz |
| Gain Settings | 40dB, 50dB, 60dB (via onboard resistors) |
| AGC Attack/Release Ratios | 1:4000 (default), configurable via AR pin |
Pinout Description
| Pin | Function |
|---|---|
| VDD | Power supply (2.7V–5.5V) |
| GND | Ground |
| OUT | Analog audio output (AC-coupled) |
| GAIN | Gain select (optional) |
| AR | Attack/Release ratio select |
No SHDN pin: Module is always active when powered.
Wiring Instructions
Basic Setup (Arduino or MCU):
MAX9814 → Arduino
-----------------------------
VDD → 3.3V or 5V
GND → GND
OUT → A0 (Analog Input)
GAIN → Leave floating or configure
AR → Leave floating or configureFor audio visualization or sound triggers, use analogRead() on OUT and apply threshold logic.
Gain Configuration
| GAIN Pin Connection | Resulting Gain |
|---|---|
| Floating | 60dB |
| Tied to GND | 50dB |
| Tied to VDD | 40dB |
Some variants use onboard resistors to fix gain—check your PCB layout.
AGC Attack/Release Ratio
| AR Pin Connection | Ratio |
|---|---|
| Floating | 1:4000 |
| Tied to GND | 1:2000 |
| Tied to VDD | 1:500 |
Testing Procedure
- Power the module with 3.3V or 5V.
- Connect OUT to an oscilloscope or ADC.
- Speak near the mic and observe dynamic gain adjustment.
- Adjust GAIN and AR pins to test different profiles.
Integration Tips
- For embedded systems, buffer the output with an op-amp if driving long traces.
- For audio-reactive lighting, use analog thresholds or FFT on sampled data.
- For biomedical sensing, consider shielding and filtering to reduce ambient noise.
References