40

30

R =

L

50kΩ

20

10

R =

L

5kΩ

0

R =

L

500kΩ

–10

–20

C =

L

10nF

C =

L

1nF

C =

L

100pF

100

1k

10k

100k

1M

10M

Frequency (Hz)

INA138, INA168

www.ti.com

SBOS122D – DECEMBER 1999 – REVISED DECEMBER 2014

Typical Applications (continued)

8.2.2.2 Detailed Design Procedure

A low-pass filter can be formed at the output of the INA138 or INA168 devices simply by placing a capacitor of

the desired value in parallel with the load resistor. First determine the value of the load resistor needed to

achieve the desired gain. Refer to the table in Figure 9. Next, determine the capacitor value that will result in the

desired cutoff frequency according to the equation shown in Figure 12. Figure 13 illustrates various combinations

8.2.2.3 Application Curve

Figure 13. Gain vs Frequency

8.2.3 Offsetting the Output Voltage

For many applications using only a single power supply it may be required to level shift the output voltage away

from ground when there is no load current flowing in the shunt resistor. Level shifting the output of the INA138 or

INA168 devices is easily accomplished by one of two simple methods shown in Figure 14. The method on the

left hand side of Figure 14 illustrates a simple voltage divider method. This method is useful for applications that

require the output of the INA138 or INA168 devices to remain centered with respect to the power supply at zero

require a fixed value of output offset, independent of the power supply voltage, the current source method shown

on the right-hand side of Figure 14 is recommended. With this method a REF200 constant current source is used

Copyright © 1999–2014, Texas Instruments Incorporated

Submit Documentation Feedback

13

Product Folder Links: INA138 INA168