INA217AIP datasheet(14/25 Pages) TI1

14 / 25 page

Frequency (Hz)

5000

10000

15000

20000

0.0005

0.0007

0.001

0.002

0.003

0.005

0.007

0.01

0.02

0.03

0.05

D001

Gain = 20 dB

Gain = 40 dB

Gain = 60 dB

INA217

SBOS247C – JUNE 2002 – REVISED NOVEMBER 2015

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Typical Application (continued)

R4 and R5 provide a path for input bias current of the INA217. Input offset current (typically 100 nA) creates a DC

differential input voltage that will produce an output offset voltage. This is generally the dominant source of output

offset voltage in this application. With a maximum gain of 1000 (60 dB), the output offset voltage can be several

volts. This may be entirely acceptable if the output is AC-coupled into the subsequent stage. An alternate

technique is shown in Figure 16. An inexpensive FET-input operational amplifier in a feedback loop drives the

DC output voltage to 0 V. A2 is not in the audio signal path and does not affect signal quality.

Gain is set with a variable resistor, R7, in series with R6. R6 determines the maximum gain. The total resistance,

R6 + R7, determines the lowest gain. A special reverse-log taper potentiometer for R7 can be used to create a

linear change (in dB) with rotation.

8.2.3 Application Curve

Figure 17. THD + Noise for the Phantom Powered Microphone Circuit

9 Power Supply Recommendations

The INA217 is specified for operation from ±4.5 V to ±18 V; many specifications apply from –40°C to 85°C.

Parameters that can exhibit significant variance with regard to operating voltage or temperature are presented in

the Typical Characteristics.

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INA217AIP Datasheet(PDF) 14 Page - Texas Instruments