Datasheet

®
INA103
10
Figure 6 shows an active control loop that adjusts the output
offset voltage to zero. A
2
, R, and C form an integrator that
produces an offsetting voltage applied to one input of the
INA103. This produces a –6dB/octave low frequency roll-
off like the capacitor input coupling in Figure 5.
COMMON-MODE INPUT RANGE
For proper operation, the combined differential input signal
and common-mode input voltage must not cause the input
amplifiers to exceed their output swing limits. The linear
input range is shown in the typical performance curve
“Maximum Common-Mode Voltage vs Output Voltage.”
For a given total gain, the input common-mode range can be
increased by reducing the input stage gain and increasing the
output stage gain with the circuit shown in Figure 7.
OUTPUT SENSE
An output sense terminal allows greater gain accuracy in
driving the load. By connecting the sense connection at the
load, I•R voltage loss to the load is included inside the
feedback loop. Current drive can be increased by connect-
ing a current booster inside the feedback loop as shown in
Figure 11.
FIGURE 6. Automatic DC Restoration.
FIGURE 4. Output Offsetting. FIGURE 5. Input Offset Adjustment for AC-Coupled Inputs.
11
10
7
16
15
13
14
6
2
1
INA103
–In
+In
50kΩ
(1)
50kΩ
(1)
100kΩ
(1)
V
OUT
Gain = 100V/V
(40dB)
NOTE: (1) 50k R, 100k pot is
max recommended value. Use
smaller values in this ratio if possible.
ΩΩ
I
B
–
I
B
+
I
B
–
≈ I
B
+
≈ 2.5µA
11
10
7
16
15
13
14
6
2
1
INA103
–In
+In
100kΩ
(1)
V
OUT
+
–
100kΩ
(1)
10kΩ
2kΩ
100kΩ
R
C
1µF
Gain = 100V/V
(40dB)
NOTE: (1) 100k is max recommended
value. Use smaller value if possible.
Ω
1/2 OPA1013
A
2
f
–3dB
=
Gain
12π RC
11
10
7
16
15
13
14
6
2
1
INA103
150Ω
–
+
150Ω
10kΩ
OPA27
100µA
(1)
Offset Adjustment
Range = ±15mV
V–
V
OUT
V+
NOTE: (1) 1/2 REF200
100µA
(1)
∆
V
IN
Gain = 1V/V
(0dB)