Datasheet

AD830
Rev. C | Page 17 of 20
75Ω
75Ω
V
P
V
OUT
V
N
AD830
1
2
3
4
8
7
6
5
A = 1
G
M
G
M
C
0.1µF
0.1µF
V
IN
00881-044
Figure 44. Full Bandwidth Line Driver (G = +2)
SUPPLY VOLTAGE (±V)
0.05
0.01
515
DIFFERENTIAL GAIN (%)
121731
0.04
0.06
0.07
0.09
4
GAIN
PHASE
GAIN = +2
R
L
= 150Ω
FREQ = 3.58MHz
0 TO 0.7V
1110986
0.02
0.03
0.10
0.08
DIFFERENTIAL PHASE (Degrees)
0.16
0.04
0.06
0.14
0.18
0.02
0.12
0.10
0.08
0.20
0
0881-045
FREQUENCY (Hz)
0.2
10k
AMPLITUDE RESPONSE (dB)
–0.8
100k 1M 10M
100M
–0.7
–0.6
–0.5
–0.4
–0.3
–0.2
–0.1
0
0.1
V
S
= ±15V
R
L
= 150Ω
GAIN = +2
V
S
= ±10V
V
S
= ±5V
0
0881-046
Figure 46. 0.1 dB Gain Flatness for the Circuit of Figure 44
AC-COUPLED LINE RECEIVER
The AD830 is configurable as an ac-coupled differential
amplifier on a single- or bipolar-supply voltage. All that is
needed is inclusion of a few noncritical passive components, as
illustrated in Figure 47. A simple resistive network at the X G
M
input establishes a common-mode bias. Here, the common
mode is centered at 6 V, but in principle can be any voltage
within the common-mode limits of the AD830. The 10 k
resistors to each input bias the X G
M
stage with sufficiently high
impedance to keep the input coupling corner frequency low, but
not too large so that residual bias current induced offset voltage
becomes troublesome. For dual-supply operation, the 10 k
resistors may go directly to ground. The output common is
conveniently set by a Zener diode for a low impedance
reference to preserve the high frequency CMR. However, a
simple resistive divider works fine, and good high frequency
CMR can be maintained by placing a compensating resistor in
series with the +Y input. The excellent CMRR response of the
circuit is shown in Figure 48. A plot of the 0.1 dB flatness from
10 Hz is also shown. With the use of 10 F capacitors, the CMR
is >90 dB down to a few tens of hertz. This level of performance
is almost impossible to achieve with discrete solutions.
Figure 45. Differential Gain and Phase for the Circuit of Figure 44
75Ω
75Ω
+12
V
V
OUT
1000µF
10µF
10µF
AD830
1
2
3
4
8
7
6
5
A = 1
G
M
G
M C
0.1µF
Z
CM
75Ω
COAX
CABLE
+12V
4.7kΩ
6.8V
1N4736
INPUT
SIGNAL
R
T
10kΩ
10kΩ
2kΩ*
+V
S
10kΩ
10kΩ
*OPTIONAL TUNING FOR IMPROVING
VERY LOW FREQUENCY CMR.
00881-047
Figure 47. AC-Coupled Line Receiver