AG920-07 NVE, AG920-07 Datasheet - Page 102

• Manufacturer Part Number: AG920-07
• Description: KIT EVALUATION GT SENSOR
• Manufacturer: NVE

Specifications of AG920-07

• Sensor Type: Magnetic. GMR (Giant Magnetoresistive)
• Interface: Analog
• Embedded: No
• Utilized Ic / Part: ABL & AKL Series GT Sensors
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Supply: -
• Sensitivity: -
• Sensing Range: -
• Other names: 391-1022

Three Op Amp Bridge Amplifier
The three op-amp circuit shown in the figure below is the most robust version of an op amp
implementation. In this circuit the CMRR still depends on the resistor ratios of the differential
amplifier (U4) but is not dependent on the resistors R1, RG, and R2. Therefore to minimize common
mode errors the gain of the first stage should be made large compared to the gain of the second stage.
The minimum gain of the second stage is dependent on amplifiers U2 and U3 output voltage range and
Op Amp U4’s common-mode input range, which for the LMC7101, is rail-to-rail allowing a gain of
one (1) in the second stage.
The DC transfer function of the circuit is:
The symmetrical nature of this configuration also allows for cancellation of common mode errors in
amplifiers U2 and U3 if the errors track.
Vout
=
V
ref
4 Vin-
8 Vin+
+



+5V
1
+
C1 0.1uF
5 Vout+
1 Vout-
2R
R
G
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1
T






HREE
R
R
3 +
2 -
4
3
3 +
2 -
RG



V
LMC7101A/NS
LMC7101A/NS
O
IN
P
+5V
+5V
U2
U3
R2
A
for R
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R1
7 V+
4 V-
7 V+
4 V-
MP
C2 0.1uF
C3 0.1uF
1
P
= R
- 102 -
6
6
REAMPLIFIER
2
, R
3
R4
R3
= R
Vref
5
, R
3 +
2 -
R6
4
LMC7101A/NS
= R
C
Application Notes
+5V
IRCUIT
U4
6
R5
7 V+
4 V-
and V
C4 0.1uF
6
IN
=(V
out+
) - (V
Vout
out-
)