+5V
0.1µF
0.1µF
1
VREF
8
V+
7
6
5
DCLOCK
DOUT
500Ω
+In
2
Serial
Interface
ADS7822
12-Bit ADC
OPA347
VIN
–In
CS/SHDN
3
3300pF
GND
4
VIN = 0V to 5V for
0V to 5V output.
NOTE: ADC Input = 0V to VREF
RC network filters high-frequency noise.
FIGURE 8. OPA347 in Noninverting Configuration Driving ADS7822.
V+ = +2.7V to 5V
Passband 300Hz to 3kHz
R9
510kΩ
R1
R4
R2
1.5kΩ
20kΩ
1MΩ
C3
C
1
33pF
1000pF
R7
51kΩ
R8
150kΩ
V
8
+
1
VREF
1/2
7
6
DCLOCK
DOUT
OPA2347
+IN
2
–IN
1/2
OPA2347
R3
1MΩ
ADS7822
12-Bit A/D
Electret
Microphone(1)
Serial
Interface
C2
1000pF
R6
100kΩ
5
CS/SHDN
3
4
G = 100
NOTE: (1) Electret microphone
powered by R1.
R5
20kΩ
GND
FIGURE 9. Speech Bandpass Filtered Data Acquisition System.
OPA347, 2347, 4347
10
SBOS167D
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