OPA330

+5 V

+5 V

R

G

INA827

V

IN-

V

IN+

REF

V

OUT

+5 V

a) Level shifting using the OPA330 as a low-impedance buffer

b) Level shifting using the low-impedance output of the REF3225

+5 V

+5 V

R

G

INA827

V

IN-

V

IN+

REF

V

OUT

REF3225

+2.5 V

Copyright © 2016, Texas Instruments Incorporated

21

INA827

www.ti.com

SBOS631B – JUNE 2012 – REVISED NOVEMBER 2017

Product Folder Links: INA827

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Copyright © 2012–2017, Texas Instruments Incorporated

7.3.7 Reference Pin

The INA827 output voltage is developed with respect to the voltage on the reference pin. Often, in dual-supply

operation, the reference pin (pin 6) is connected to the low-impedance system ground. Offsetting the output

signal to a precise mid-supply level (for example, 2.5 V in a 5-V supply environment) can be useful in single-

supply operation. The signal can be shifted by applying a voltage to the device REF pin, which can be useful

when driving a single-supply ADC.

For best performance, keep any source impedance to the REF pin below 5 Ω. Referring to Figure 61, the

reference resistor is at one end of a 50-kΩ resistor. Additional impedance at the REF pin adds to this 50-kΩ

resistor. The imbalance in resistor ratios results in degraded common-mode rejection ratio (CMRR).

Figure 59 shows two different methods of driving the reference pin with low impedance. The OPA330 is a low-

power, chopper-stabilized amplifier and therefore offers excellent stability over temperature. The OPA330 is

available in the space-saving SC70 and even smaller chip-scale package. The REF3225 is a precision reference

in a small SOT23-6 package.

Figure 59. Options for Low-Impedance Level Shifting

7.3.8 Dynamic Performance

Figure 19 illustrates that, despite having low quiescent current of only 200 µA, the INA827 achieves much wider

bandwidth than other instrumentation amplifiers (INAs) in its class. This achievement is a result of using TI’s

proprietary high-speed precision bipolar process technology. The current-feedback topology provides the INA827

with wide bandwidth even at high gains. Settling time also remains excellent at high gain because of a 1.5-V/µs

high slew rate.