INA821 datasheet(30/43 Pages) TI2

30 / 43 page

C001

-20

-10

Input Current (mA)

C001

-10

-5

Input Voltage (V)

50 k

10.5 k

G 1

5.75 1

OUT

REF

G =

= 5.75

4.8 V

2.5 V

400 mV

R + R

V = V

= 4.167 kW

INA818

SBOS894A – APRIL 2019 – REVISED JUNE 2019

www.ti.com

Product Folder Links: INA818

Submit Documentation Feedback

Typical Applications (continued)

R1 sets the input impedance of the voltage input mode. The minimum typical input impedance is 100 kΩ. 100 kΩ

is selected for R1 because increasing the R1 value also increases noise. The value of R3 must be extremely

small compared to R1 and R2. 20 Ω for R3 is selected because that resistance value is much smaller than R1 and

yields an input voltage of ±400 mV when operated in current mode (±20 mA).

Use Equation 5 to calculate R2 given VD = ±400 mV, VIN = ±10 V, and R1 = 100 kΩ.

(5)

The value obtained from Equation 5 is not a standard 0.1% value, so 4.17 kΩ is selected. R1 and R2 also use

0.1% tolerance resistors to minimize error.

Use Equation 6 to calculate the ideal gain of the instrumentation amplifier.

(6)

Equation 7 calculates the gain-setting resistor value using the INA818 gain equation, Equation 1.

(7)

10.5 kΩ is a standard 0.1% resistor value that can be used in this design.

9.2.1.3 Application Curves

Figure 70 and Figure 71 show typical characteristic curves for the circuit in Figure 69.

Figure 70. PLC Output Voltage vs Input Voltage

Figure 71. PLC Output Voltage vs Input Current

INA821 Datasheet(PDF) 30 Page - Texas Instruments

INA821 Datasheet(HTML) 30 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Datasheet Download

Link URL