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Microphone Amplifier with AGC and Low-Noise Microphone Bias

Integrated Automatic Gain Control Solves Audio Output Level Fluctuations

Product Details

Key Features

Parametric specs for Microphone Amplifiers
# Channels 1
VSUPPLY (V) (min) 2.7
VSUPPLY (V) (max) 5.5
IQ (mA) (typ) 3.1
THD+N (%) 0.04
en (nV/√Hz) 30
PSRR (dB) (min) 55
Input Type Single Ended
Package/Pins TDFN/14
Budgetary
Price (See Notes)
0.7
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Simplified Block Diagram

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Parameters

Parametric specs for Microphone Amplifiers
# Channels 1
VSUPPLY (V) (min) 2.7
VSUPPLY (V) (max) 5.5
IQ (mA) (typ) 3.1
THD+N (%) 0.04
en (nV/√Hz) 30
PSRR (dB) (min) 55
Input Type Single Ended
Package/Pins TDFN/14
Budgetary
Price (See Notes)
0.7

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

Applications/Uses

  • 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

Description

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.

Simplified Block Diagram

MAX9814: Simplified Application Circuit/Functional Diagram MAX9814: Simplified Application Circuit/Functional Diagram Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .