Datasheet

AD830
Rev. C | Page 15 of 20
V
P
V
OUT
AD830
1
2
3
4
8
7
6
5
A = 1
C
V
ICM
V
IN
V
OCM
V
OUT
= (V
IN
– V
ICM
) + V
OCM
G
M
G
M
00881-035
Figure 35. General Single-Supply Connection
DIFFERENTIAL INPUTVOLTAGE (V
PEAK
)
16
0
0
COMMON-MODE VOLTAGE LIMITS (±V)
0.4 1.2 1.60.8
8
4
12
2.0
V
P
= +30V
V
P
= +15V
V
P
= +10V
TO GND
20
24
28
30
00881-036
Figure 36. Input Common-Mode Range for Single Supply
SUPPLY VOLTAGE (V)
16
0
3010
MAXIMUM OUTPUT SWING (±V)
14 18 22 26
8
4
12
20
24
28
TO V
P
TO GND
0
0881-037
Figure 37. Output Swing Limit for Single Supply
Differential Line Receiver
The AD830 is specifically designed to perform as a differential
line receiver. The circuit in Figure 38 shows how simple it is to
configure the AD830 for this function. The signal from System A is
received differentially relative to the common of System A, and
that voltage is exactly reproduced relative to the common in
System B. The common-mode rejection versus frequency, shown
in Figure 6, is excellent, typically 100 dB at low frequencies.
The high input impedance permits the AD830 to operate as a
bridging amplifier across low impedance terminations with
negligible loading. The differential gain and phase specifications
are very good, as shown in Figure 12 for 500  and Figure 15
for 150 . The input and output common should be separated
to achieve the full CMR performance of the AD830 as a
differential amplifier. However, a common return path is
necessary between System A and System B.
COMMON IN
SYSTEM A
V
N
AD830
1
2
3
4
8
7
6
5
A = 1
G
M
G
M
C
V
CM
Z
CM
COMMON IN
SYSTEM B
V
P
V
OUT
0.1µF
0.1µF
INPUT
SIGNAL
V
1
V
2
V
OUT
= V
1
– V
2
0
0881-038
Figure 38. Differential Line Receiver
Wide Range Level Shifter
The wide common-mode range and accuracy of the AD830
allows easy level shifting of differential signals referred to an
input common-mode voltage to any new voltage defined at the
output. The inputs may be referenced to levels as high as 10 V at
the inputs with a ±2 V swing around 10 V. In the circuit in
Figure 39, the output voltage, V
OUT
, is defined by the simple
equation shown below. The excellent linearity and low distortion
are preserved over the full input and output common-mode
range. The voltage sources need not be of low impedance, since
the high input resistance and modest input bias current of the
AD830 V-to-I converters permit the use of resistive voltage
dividers as reference voltages.
G
M
V
P
V
OUT
INPUT
COMMON
V
N
0.1µF
AD830
1
2
3
4
8
7
6
5
A = 1
C
0.1µF
INPUT
SIGNAL
V
1
V
2
OUTPUT
COMMON
V
3
V
OUT
= V
1
– V
2
+ V
3
00881-039
G
M
Figure 39. Differential Amplification with Level Shifting
Difference Amplifier with Gain > 1
The AD830 can provide instrumentation amplifier style and
differential amplification at gains greater than 1. The input
signal is connected differentially and the gain is set via feedback
resistors, as shown in Figure 40. The gain is G = (R
2
+ R
1
)/R
2
.
The AD830 can provide either inverting or noninverting
differential amplification. The polarity of the gain is established
by the polarity of the connection at the input. Feedback resistor,
R
2
, should generally be R
2
≤ 1 k to maintain closed-loop