Datasheet

OPA330
+5V
+5V
R
G
INA826
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
INA826
V
IN-
V
IN+
REF
V
OUT
REF3225
+2.5V
INA826
SBOS562E –AUGUST 2011–REVISED APRIL 2013 www.ti.com
REFERENCE TERMINAL
The output voltage of the INA826 is developed with respect to the voltage on the reference terminal. Often, in
dual-supply operation, the reference pin (pin 6) is connected to the low-impedance system ground. In single-
supply operation, it can be useful to offset the output signal to a precise mid-supply level (for example,
2.5 V in a 5-V supply environment). To accomplish this, a voltage source can be tied to the REF pin to level-shift
the output so that the INA826 can drive a single-supply ADC, for example.
For the best performance, source impedance to the REF terminal should be kept below 5 Ω. As can be seen in
Figure 58, 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 the resistor ratios results in degraded common-mode rejection ratio
(CMRR).
Figure 62 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. It is available in the
space-saving SC70 and even smaller chip-scale package. The REF3225 is a precision reference in the small
SOT23-6 package.
Figure 62. Options for Low-Impedance Level Shifting
DYNAMIC PERFORMANCE
The typical characteristic curve Gain vs Frequency (Figure 23) illustrates that, despite its low quiescent current of
only 200 µA, the INA826 achieves much wider bandwidth than other 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 INA826 with wide bandwidth even at high gains. Settling time also remains excellent at high gain
because of a high slew rate of 1 V/µs.
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