MAX9814 Microphone Amplifier

By Maxim Integrated 529

MAX9814 Microphone Amplifier

Maxim's 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 12 dB gain, while the VGA gain automatically adjusts from 20 dB to 0 dB, depending on the output voltage and the AGC threshold. The output amplifier offers selectable gains of 8 dB, 18 dB, and 28 dB. With no compression, the cascade of the amplifiers results in an overall gain of 40 dB, 50 dB, or 60 dB. 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 30 ms. The low-noise microphone-bias-voltage generator can bias most electret microphones.

  • Automatic gain control (AGC)
  • Three gain settings (40 dB, 50 dB, 60 dB)
  • Programmable attack time
  • Programmable attack and release ratio
  • 2.7 V to 5.5 V supply voltage range
  • Low input-referred noise density of 30 nV/√ Hz
  • Low THD: 0.04% (typ.)
  • Low-power shutdown mode
  • Bluetooth® headsets
  • Digital still cameras
  • Digital video cameras
  • Entertainment systems (for example: karaoke)
  • High-quality portable recorders
  • IP phones/telephone conferencing
  • PDAs
  • Two-way communicators

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