Datasheet

MAX4063
Differential Microphone Preamplifier with
Internal Bias and Complete Shutdown
8 _______________________________________________________________________________________
book PCs or PDAs. Used correctly, the advantages
over a single-ended solution are:
• Better power-supply noise rejection.
• Less degradation from noise in PC board ground
planes.
• The microphone and preamplifier may be placed
physically further apart, easing PC board layout
restrictions.
Differential-Gain Adjustment
The MAX4063 allows the user to alter the differential
gain to optimize the signal-to-noise ratio (SNR) of their
system. The gain is set by a single external resistor
(R
G
) connected between the G1 and G2 pins:
where A
V
is the required voltage gain.
Hence, an 11.11kΩ resistor yields a gain of 20V/V, or
26dB. Leaving the pins unconnected results in a gain of
2V/V. Gain is defined as:
For differential out:
The resistor can be either fixed or variable, allowing the
use of a digitally controlled potentiometer to alter the
gain under software control.
Auxiliary Input-Gain Adjustment
The MAX4063 provides an option to increase the
AUX_IN (see Figure 3). To increase the gain, connect
resistor R
ADJ
between the ADJ and AUX_IN pins. R
ADJ
is
calculated from the following formula:
R
2M
AV
ADJ
AUX
=
−
Ω
20
()to increase the gain
A
V
V
VD
OUT OUT
IN+ IN-
=
−
−
V
V
R
200k
A
G
VD
=
−
Ω
2
BIAS
BIAS
AUX_IN
12
IN-
IN+
10
9
6
V
CC
2.4V TO 5.5V
MAX4063
2INT/AUX
8OUT
OUT
ADJ
4
7
GND
11
SHDN
SHDN
V
CC
3
BIAS
5
V
BIAS
G2
G1
1
14
R
G
Functional Diagram