MAX4194(1999) 查看數據表（PDF） - Maxim Integrated

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MAX4194
(Rev.:1999)

Micropower, Single-Supply, Rail-to-Rail, Precision Instrumentation Amplifiers

Maxim Integrated 

Micropower, Single-Supply, Rail-to-Rail,

Precision Instrumentation Amplifiers

Power-Supply Bypassing and Layout

Good layout technique optimizes performance by

decreasing the amount of stray capacitance at the

instrumentation amplifier’s gain-setting pins. Excess

capacitance will produce peaking in the amplifier’s fre-

quency response. To decrease stray capacitance, min-

imize trace lengths by placing external components as

close to the instrumentation amplifier as possible. For

best performance, bypass each power supply to

ground with a separate 0.1µF capacitor.

Transducer Applications

The MAX4194–MAX4197 instrumentation amplifiers can

be used in various signal-conditioning circuits for ther-

mocouples, PT100s, strain gauges (displacement sen-

sors), piezoresistive transducers (PRTs), flow sensors,

and bioelectrical applications. Figure 7 shows a simpli-

fied example of how to attach four strain gauges (two

identical two-element strain gauges) to the inputs of the

MAX4194. The bridge contains four resistors, two of

which increase and two of which decrease by the same

ratio.

With a fully balanced bridge, points A (IN+) and B (IN-)

see half the excitation voltage (VBRIDGE). The low

impedance (120Ω to 350Ω) of the strain gauges, how-

ever, could cause significant voltage drop contributions

by the wires leading to the bridge, which would cause

excitation variations. Output voltage VOUT can be cal-

culated as follows:

VOUT = VAB · G

where G = (1 + 50kΩ / RG) is the gain of the instrumen-

tation amplifier.

Since VAB is directly proportional to the excitation, gain

errors may occur.

RG

REFERENCE

VBRIDGE

RG+

IN+

R

VAB = VIN+ - VIN-

R

IN-

RG-

OUT

MAX144

ADC

µP

REF

R = 120Ω - 350Ω

A

B

VEE

VCC

R

R

Figure 7. Strain Gauge Connection to the MAX4194

___________________Chip Information

TRANSISTOR COUNT: 432

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