Texas Instruments INA1620EVM, User Manual, Page: 4 / 24

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Modifications
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4 SBOU205 – March 2018
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INA1620EVM Audio Amplifier Evaluation Module
3.1 Gain
Equation 1 and Equation 2 display the transfer function of the circuit shown in Figure 1 .
(1)
(2)
When using the internal thin-film resistors, all resistance values in Equation 1 and Equation 2 are 1 k
Ω
.
This simplifies Equation 1 and Equation 2 into Equation 3 .
(3)
The INA1620EVM also allows the use of external resistors to set the amplifier gain. Note that external
resistors must be used if the thin-film resistors in the INA1620 are to be used for other purposes.
Equation 4 and Equation 5 display the transfer function for the circuit shown in Figure 2 .
Figure 2. INA1620EVM Schematic Using External Resistors
(4)
(5)
For best CMRR performance, it is desirable to balance the gain from the IN+ and IN– components by
setting R1 = R7, R13 = R19, R2 = R6, and R20 = R5. For a typical headphone amplifier application, both
the left and right channels will be identical, so R1 = R7 = R13 = R19 and R2 = R6 = R15 = R20. In this
case,
Equation 4 and Equation 5 simplify to Equation 6 .
(6)