COM

IN-

IN+

500

k

500

k

Copyright © 2016, Texas Instruments Incorporated

C

IN

IN

IN

IN

1

1

F

C

2

R

C

2

(2 R )

2

˜ S ˜

˜

˜ S ˜

˜

˜

COM

IN-

IN+

500

k

500

k

Copyright © 2016, Texas Instruments Incorporated

VMID(OUT)

21

INA1650

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SBOS818 – DECEMBER 2016

Product Folder Links: INA1650

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Copyright © 2016, Texas Instruments Incorporated

Application Information (continued)

Figure 47. AC-Coupling Capacitors Charge to the Midsupply Voltage Through the Input Resistors

8.1.4 Input AC Coupling

The signal path in most audio systems is typically AC-coupled to avoid the propagation of DC voltages, which

can potentially damage loudspeakers or saturate power amplifiers. The capacitor values must be selected to

pass the desired bandwidth of audio signals. The high-pass corner frequency is calculated with Equation 5:

(5)

Figure 48. AC-Coupling Capacitors Form a High-Pass Filter With INA1650 Input Resistors

Although the input resistors of the INA1650 are matched typically within 0.01%, large capacitors are usually

mismatched. The mismatch in the values of the AC-coupling capacitors causes the corner frequencies at the two

signal inputs (IN+ and IN–) to be different, which can degrade CMRR at low frequency. For this reason, TI

recommends placing the high-pass corner frequency well below the audio bandwidth and to use a resistor in

section for more information on placing a resistor in series with the COM pin. Figure 49 shows the effect of a 5%

at 100 Hz: 1-µF AC-coupling capacitors with a 5% mismatch degrade the CMRR to 75 dB, while 10-µF