Datasheet

Data Sheet AD8250
Rev. C | Page 21 of 24
DATA ACQUISITION
The AD8250 makes an excellent instrumentation amplifier for
use in data acquisition systems. Its wide bandwidth, low distortion,
low settling time, and low noise enable it to condition signals in
front of a variety of 16-bit ADCs.
Figure 59 shows a schematic of the AD825x data acquisition
demonstration board. The quick slew rate of the AD8250 allows
it to condition rapidly changing signals from the multiplexed
inputs. An FPGA controls the AD7612, AD8250, and ADG1209.
In addition, mechanical switches and jumpers allow users to pin
strap the gains when in transparent gain mode.
This system achieved −111 dB of THD at 1 kHz and a signal-to-
noise ratio of 91 dB during testing, as shown in Figure 58.
0
–140
–130
–120
–110
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0 5 10 15 20 25 30 35 40 45 50
AMPLITUDE (dB)
FREQUENCY (kHz)
06288-066
Figure 58. FFT of the AD825x DAQ Demo Board Using the AD8250,
1 kHz Signal
06288-065
AD8250
2
+IN
–IN
A1
A0
OUT
REF
–V
S
+V
S
DGND
5
3
4
9
1
7
10
11
12
13
14
15
16
6
2
S1A
EN
S2A
S3A
S4A
S1B
S2B
DB
GND
DA
S3B
S4B
A0
A1
V
SS
V
DD
JMP
JMP
JMP
+12V
–12V
+12V
–12V
JMP
JMP
–V
S
+5V
+5V
DGND
806Ω
806Ω
806Ω
806Ω
806Ω
806Ω
806Ω
806Ω
0Ω
0Ω
49.9Ω
0Ω
–CH1
+CH1
+CH2
–CH2
+CH3
–CH3
+CH4
–CH4
1nF
2kΩ
2kΩ
0.1µF
GND
+12V
–12V
+
+
10µF
10µF
0.1µF
C
D
C
C
C
C
C3
0.1µF
C4
0.1µF
+5V
+5V
DGND
DGND
R8
2kΩ
+IN
AD7612
ADR435
ADG1209
DGND
ALTERA
EPF6010ATC144-3
8
0Ω
0Ω
1
10
6
WR
9
4
5
8
3
7
+
–
DGND
2k
Ω
DGND
Figure 59. Schematic of ADG1209, AD8250, and AD7612 in the AD825x DAQ Demo Board