MAX9814：Microphone Amplifier with AGC and Low-Noise Microphone Bias

Integrated Automatic Gain Control Solves Audio Output Level Fluctuations

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.

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

MAX9814: Simplified Application Circuit/Functional Diagram

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

DataSheet

title	Download file
MAX9814 Data Sheet	MAX9814.pdf

Parametrics

Part Number	Channels	V_SUPPLY (V)	V_SUPPLY (V)	I_Q (mA)	THD+N (%)	e_n (nV/√Hz)	PSRR (dB)	Input Type	Ext. Gain	Fxd. Gain (\|V/V\|)	Fxd. Gain (\|V/V\|)	Microphone Bias	Package/Pins	Budgetary Price
Part Number	Channels	min	max	typ	THD+N (%)	e_n (nV/√Hz)	min	Input Type	Ext. Gain	min	max	Microphone Bias	Package/Pins	See Notes
MAX9814	1	2.7	5.5	3.1	0.04	30	55	Single Ended	No	100	1000	Yes	TDFN-EP/14	$0.63 @1k