±10

0

10

20

30

40

±6

±5

±4

±3

±2

±1

0

1

2

3

4

5

6

Input Voltage (V)

C01

0.00

0.25

0.50

0.75

1.00

1.25

±6

±5

±4

±3

±2

±1

0

1

2

3

4

5

6

Input Voltage (V)

C01

±150

±125

±100

±75

±50

±25

0

25

50

±6

±5

±4

±3

±2

±1

0

1

2

3

4

5

6

Input Voltage (V)

C01

_

3dB A1

6

2

1

f

0.144 Hz

R

2

C

2

S

§

·

˜

˜

˜

¨

¸

©

¹

17

REF3312, REF3318, REF3320, REF3325, REF3330, REF3333

www.ti.com

SBOS392H – AUGUST 2007 – REVISED AUGUST 2019

Product Folder Links: REF3312 REF3318 REF3320 REF3325 REF3330 REF3333

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Copyright © 2007–2019, Texas Instruments Incorporated

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In applications that cannot tolerate such a low-frequency cutoff, and therefore a long start-up time, buffer the A1–

input with another OPA317 to properly drive the ADC input with a lower-input capacitor.

10.2.1.2.7

Passive Component Tolerances and Materials

Resistors R1, R2, R3, R4, R5, R6, and R7 directly affect the accuracy of the circuit. To meet the unadjusted

accuracy goals of 0.2%, the resistors used are 0.1%. Select 0.1% resistors for the construction of the difference

amplifier circuit to provide a common-mode rejection ratio (CMRR) of at least 60 dB.

10.2.1.3 Application Curves

10.2.1.3.1

DC Performance

The measured dc performance and calculated error of the circuit is shown in Figure 20 and Figure 21,

respectively. By applying a two-point gain and offset calibration over the specified ±5-V input range, the

calibrated error is shown in Figure 22. The uncalibrated results show errors of 138 μV, or 0.0138%FSR. The

calibrated results with a simple two-point calibration show errors under 5 μV, or 0.0005%FSR, in the specified

input range of ±5 V.

Figure 20. Measured DC Transfer Function with ±6-V Input

Figure 21. Measured Output Error with ±6-V Input

Figure 22. Calibrated Output Error with ±6-V Input