OPA376-Q1_016 Datasheet, PDF (19/39 Pages) Texas Instruments – Low-Noise, Low Quiescent Current, Precision Operational Amplifier e-trim Series

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OPA376-Q1, OPA2376-Q1, OPA4376-Q1
SBOS549B – APRIL 2011 – REVISED JUNE 2016
Application Information (continued)
8.1.4 Phantom-Powered Microphone
The circuit shown in Figure 28 depicts how a remote microphone amplifier can be powered by a phantom source
on the output side of the signal cable. The cable serves double duty, carrying both the differential output signal
from and dc power to the microphone amplifier stage.
An OPA2376-Q1 serves as a single-ended input to a differential output amplifier with a 6-dB gain. Common-
mode bias for the two op amps is provided by the dc voltage developed across the electret microphone element.
A 48-V phantom supply is reduced to 5.1 V by the series 6.8-kΩ resistors on the output side of the cable, and the
4.7-kΩ resistors and zener diode on the input side of the cable. AC coupling blocks the different dc voltage levels
from each other on each end of the cable.
An INA163 instrumentation amplifier provides differential inputs and receives the balanced audio signals from the
cable.
The INA163 gain may be set from 0 dB to 80 dB by selecting the R_G value. The INA163 circuit is typical of the
input circuitry used in mixing consoles.
Panasonic
WM-034CY
Microphone
R₁
2.7kW
1/2
OPA2376
1kW
1kW
10kW
+
10mF
1/2
OPA2376
100W
33mF
D₁
5.1V
Phantom Power
(Provides power source for microphone)
48V
1mF
C₂
R₆
33mF 100W
C₃
R₇
33mF 100W
R₈
4.7kW
R₉
4.7kW
2
3
1
2
3
1
Low-level differential audio signal
is transmitted differentially on the
same cable as power to the microphone.
R₁₀
6.8kW
R₁₁
6.8kW
10mF
10mF
+15V
R_G
INA163
3.3kW
3.3kW
-15V
Typical microphone input circuit used in mixing consoles.
Figure 28. Phantom-Powered Electret Microphone
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