Microphone Amplifier with AGC and Low-Noise Microphone Bias

Integrated Automatic Gain Control Solves Audio Output Level Fluctuations

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The MAX9814 is a low-cost, high-quality microphone amplifier with automatic gain control (AGC) and low-noise microphone bias. The device features a low-noise preamplifier, variable gain amplifier (VGA), output amplifier, microphone-bias-voltage generator and AGC control circuitry.

The low-noise preamplifier has a fixed 12dB gain, while the VGA gain automatically adjusts from 20dB to 0dB, depending on the output voltage and the AGC threshold. The output amplifier offers selectable gains of 8dB, 18dB, and 28dB. With no compression, the cascade of the amplifiers results in an overall gain of 40dB, 50dB, or 60dB. A trilevel digital input programs the output amplifier gain. An external resistive divider controls the AGC threshold and a single capacitor programs the attack/release times. A trilevel digital input programs the ratio of attack-to-release time. The hold time of the AGC is fixed at 30ms. The low-noise microphone-bias-voltage generator can bias most electret microphones.

The MAX9814 is available in the space-saving, 14-pin TDFN package. This device is specified over the -40°C to +85°C extended temperature range.
MAX9814: Simplified Application Circuit/Functional Diagram MAX9814: Simplified Application Circuit/Functional Diagram Enlarge+

Key Features

  • Automatic Gain Control (AGC)
  • Three Gain Settings (40dB, 50dB, 60dB)
  • Programmable Attack Time
  • Programmable Attack and Release Ratio
  • 2.7V to 5.5V Supply Voltage Range
  • Low Input-Referred Noise Density of 30nV/
  • Low THD: 0.04% (typ)
  • Low-Power Shutdown Mode
  • Internal Low-Noise Microphone Bias, 2V
  • Available in the Space-Saving, 14-Pin TDFN (3mm × 3mm) Package
  • -40°C to +85°C Extended Temperature Range


  • Bluetooth® Headsets
  • Digital Still Cameras
  • Digital Video Cameras
  • Entertainment Systems (e.g. Karaoke)
  • High-Quality Portable Recorders
  • IP Phones/Telephone Conferencing
  • PDAs
  • Two-Way Communicators

See parametric specs for Microphone Amplifiers (10)

Part NumberChannelsVSUPPLY
Input TypeExternal GainFxd. Gain
Fixed Gain
Microphone BiasPackage/PinsBudgetary
minmaxtypminminmaxSee Notes
MAX9814 EndedNo1001000Yes
$0.66 @1k

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX9814EVKIT: Evaluation Kit for the MAX9814
Product Reliability Reports: MAX9814.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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