INA819 datasheet(21/43 Pages) TI1

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Frequency (Hz)

100

120

140

10M

100M

10G

Frequency (Hz)

100

120

140

10M

100M

10G

EMIRR (dB)

RF _ PEAK

100 mV

INA819

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SBOS959 – DECEMBER 2018

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8.3.1.1 Gain Drift

The stability and temperature drift of the external gain setting resistor (RG ) also affects gain. The contribution of

RG to gain accuracy and drift is determined from Equation 1.

The best gain drift of 5 ppm/

℃ (maximum) is achieved when the INA819 uses G = 1 without RG connected. In

this case, gain drift is limited by the mismatch of the temperature coefficient of the integrated 40-kΩ resistors in

the differential amplifier (A3). At gains greater than 1, gain drift increases as a result of the individual drift of the

25-kΩ resistors in the feedback of A1 and A2, relative to the drift of the external gain resistor (RG.) The low

temperature coefficient of the internal feedback resistors improves the overall temperature stability of applications

using gains greater than 1 V/V over alternate solutions.

Low resistor values required for high gain make wiring resistance important. Sockets add to the wiring resistance

and contribute additional gain error (such as a possible unstable gain error) at gains of approximately 100 or

greater. To ensure stability, avoid parasitic capacitance of more than a few picofarads at RG connections. Careful

matching of any parasitics on the RG pins maintains optimal CMRR over frequency; see Figure 17.

8.3.2 EMI Rejection

Texas Instruments developed a method to accurately measure the immunity of an amplifier over a broad

frequency spectrum extending from 10 MHz to 6 GHz. This method uses an EMI rejection ratio (EMIRR) to

quantify the ability of the INA819 to reject EMI. The offset resulting from an input EMI signal is calculated using

Equation 2:

where

•

VRF_PEAK is the peak amplitude of the input EMI signal.

(2)

Figure 56 and Figure 57 show the INA819 EMIRR graph for differential and common-mode EMI rejection across

this frequency range. Table 3 lists the EMIRR values for the INA819 at frequencies commonly encountered in

real-world applications. Applications listed in Table 3 are centered on or operated near the frequency shown.

Depending on the end-system requirements, additional EMI filters may be required near the signal inputs of the

system, and incorporating known good practices such as using short traces, low-pass filters, and damping

resistors combined with parallel and shielded signal routing may be required.

Figure 56. Common-Mode EMIRR Testing

Figure 57. Differential Mode EMIRR Testing

Table 3. INA819 EMIRR for Frequencies of Interest

FREQUENCY

APPLICATION OR ALLOCATION

DIFFERENTIAL

EMIRR

COMMON-MODE

EMIRR

400 MHz

Mobile radio, mobile satellite, space operation, weather, radar, ultrahigh-

frequency (UHF) applications

52 dB

80 dB

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