Datasheet

MPLAB
®
STARTER KIT FOR
INTELLIGENT.INTEGRATED.ANALOG
USER’S GUIDE
 2013 Microchip Technology Inc. DS50002172A-page 39
Appendix C. Optional Microphone Amplifier
By default, the electret microphone on the MPLAB Starter Kit for
Intelligent.Integrated.Analog is configured as a simple audio detector; it does not pro-
vide sufficient amplification for voice or more advanced audio applications. To achieve
better performance, a microphone amplifier needs to be implemented. The preferred
design would be an AC-coupled amplifier with a gain of approximately 20:1, with the
output DC-biased to 1.6V.
Figure C-1 shows a suggested implementation for this type of amplifier. Table C-1
provides the list of required components. The exact implementation in hardware is left
to the user.
FIGURE C-1: MICROPHONE AMPLIFIER SCHEMATIC
TABLE C-1: MICROPHONE AMPLIFIER COMPONENT LIST
Component Description
C1 10 µF, 16 WVDC Electrolytic Capacitor
R1 220, Resistor (±5% tolerance or better)
(1)
R2 10 k Trim Potentiometer
U1 MCP6921-E/OT Operational Amplifier (SOT-23 package)
(1)
Note 1: Specific part options depend on your choices for implementing the design. SOT-23
packaging options are shown for convenience; other options are available.
3
4
1
2
5
U1
MCP6291
C1
R1
220
10 µF
R2
10 k
MIC_OUT
+
3.3V
(J8, Pin 5)
PREAMP_OUT