OPA376 Datasheet, PDF (19/42 Pages) Burr-Brown (TI) – Precision, Low Noise, Low Quiescent Current, Operational Amplifier

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OPA376, OPA2376, OPA4376
SBOS406G – JUNE 2007 – REVISED DECEMBER 2015
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 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 resistor 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
R₁
1.5kW
C₁
1000pF
R₂
1MW
Electret
(1)
Microphone
R₃
1MW
V+ = +2.7V to 5V
R₄
20kW
1/2
OPA2376
R₆
100kW
R₉
510kW
R₇
51kW
R₈
150kW
C₃
33pF
1/2
OPA2376
C₂ 1000pF
R₅
20kW
G = 100
Passband 300Hz to 3kHz
V_REF 1
8 ^V+
7
+IN
ADS7822 ⁶
2
-IN
12-Bit A/D ₅
3
4
DCLOCK
D_OUT
CS/SHDN
GND
Serial
Interface
(1) Electret microphone powered by R₁.
Figure 29. OPA2376 as a Speech Bandpass-Filtered, Data Acquisition System
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