0

20

40

60

80

100

120

140

160

180

10M

100M

1G

10G

Frequency (Hz)

C035

0

20

40

60

80

100

120

140

160

10M

100M

1G

10G

Frequency (Hz)

C036

20

INA188

SBOS632 – SEPTEMBER 2015

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Product Folder Links: INA188

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Copyright © 2015, Texas Instruments Incorporated

7.3.3.3 Input Bias Current Clock Feedthrough

Zero-drift amplifiers, such as the INA188, use switching on their inputs to correct for the intrinsic offset and drift of

the amplifier. Charge injection from the integrated switches on the inputs can introduce very short transients in

the input bias current of the amplifier. The extremely short duration of these pulses prevents them from being

amplified; however, the pulses can be coupled to the output of the amplifier through the feedback network. The

most effective method to prevent transients in the input bias current from producing additional noise at the

amplifier output is to use a low-pass filter (such as an RC network).

7.3.4

EMI Rejection

The INA188 uses integrated electromagnetic interference (EMI) filtering to reduce the effects of EMI from

sources (such as wireless communications) and densely-populated boards with a mix of analog signal-chain and

digital components. The INA188 is specifically designed to minimize susceptibility to EMI by incorporating an

internal low-pass filter. Depending on the end-system requirements, additional EMI filters may be required near

the signal inputs of the system, as well as incorporating known good practices such as using short traces, low-

pass filters, and damping resistors combined with parallel and shielded signal routing. 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 INA188 ability

to reject EMI. Figure 49 and Figure 50 show the INA188 EMIRR graph for both differential and common-mode

EMI rejection across this frequency range. Table 2 shows the EMIRR values for the INA188 at frequencies

commonly encountered in real-world applications. Applications listed in Table 2 can be centered on or operated

near the particular frequency shown.

Figure 49. Common Mode EMIRR Testing

Figure 50. Differential Mode (VIN+) EMIRR Testing

Table 2. INA188 EMIRR for Frequencies of Interest

FREQUENCY

APPLICATION OR ALLOCATION

DIFFERENTIAL

(IN-P) EMIRR

COMMON-MODE

EMIRR

400 MHz

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

frequency (UHF) applications

83 dB

101 dB

900 MHz

Global system for mobile communications (GSM) applications, radio

communication, navigation, GPS (to 1.6 GHz), GSM, aeronautical mobile, UHF

applications

103 dB

118 dB

1.8 GHz

GSM applications, mobile personal communications, broadband, satellite,

L-band (1 GHz to 2 GHz)

112 dB

125 dB

2.4 GHz

802.11b, 802.11g, 802.11n, Bluetooth®, mobile personal communications,

industrial, scientific and medical (ISM) radio band, amateur radio and satellite,

S-band (2 GHz to 4 GHz)

114 dB

123 dB

3.6 GHz

Radiolocation, aero communication and navigation, satellite, mobile, S-band

110 dB

121 dB

5.0 GHz

802.11a, 802.11n, aero communication and navigation, mobile communication,

space and satellite operation, C-band (4 GHz to 8 GHz)

119 dB

123 dB