Datasheet

±10
0
10
20
30
40
±6 ±5 ±4 ±3 ±2 ±1 0 1 2 3 4 5 6
Calibrated Output Error (V)
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
Output Voltage (V)
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
Output Voltage Error (µV)
Input Voltage (V)
C01
_3dB A1
6
2
1
f 0.144 Hz
R
2 C
2
S
 
§ ·
  
¨ ¸
© ¹
REF3312 , REF3318 , REF3320 , REF3325 , REF3330 , REF3333
SBOS392D –AUGUST 2007–REVISED JUNE 2014 www.ti.com
(18)
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 R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, and R
7
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
16 Submit Documentation Feedback Copyright © 2007–2014, Texas Instruments Incorporated
Product Folder Links: REF3312 REF3318 REF3320 REF3325 REF3330 REF3333