R

5

2.2kΩ

R

6

(2)

8Ω

R

7

(3)

1.6kΩ

A1

INA217

+

47µF

R

3

47kΩ

R

2

6.8kΩ

R

1

6.8kΩ

Phantom Power

+48V

+

+

R

4

2.2kΩ

C

1

(1)

47µF

60V

C

2

(1)

47µF

60V

A2

OPA137

0.1µF

+15V

0.1µF

0.1µF

1MΩ

V

O

–15V

Optional DC

output control loop.

6

7

5

4

1

2

3

Female XLR

Connector

NOTES: (1) Use non-polar capacitors if phantom power is to be

turned off. (2) R

6 sets maximum gain. (3) R7 sets minimum gain.

(4) Optional IN4148 prevents damage due to ESD and hot-plugging.

+15V

–15V

IN4148(4)

+15V

–15V

IN4148(4)

INA217

www.ti.com

SBOS247C – JUNE 2002 – REVISED NOVEMBER 2015

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The INA217 is used in professional audio equipment such as professional microphone preamps, moving-coil

transducer amplifiers, differential receivers, and bridge transducer amplifiers.

8.2 Typical Application

Figure 16 shows a typical circuit for a professional microphone input amplifier.

Figure 16. Phantom-Powered Microphone Preamplifier

8.2.1 Design Requirements

•

48-V, Phantom powered, remotely located microphone

•

Circuitry operates from ±15-V power supplies

•

Low distortion and noise over the audio frequency band

•

Gain range from to 20 db to 60 db

8.2.2 Detailed Design Procedure

R1 and R2 provide a current path for conventional 48-V phantom power source for a remotely located

microphone. An optional switch allows phantom power to be disabled. C1 and C2 block the phantom power

voltage from the INA217 input circuitry. Non-polarized capacitors should be used for C1 and C2 if phantom power

is to be disabled. For additional input protection against ESD and hot-plugging, four IN4148 diodes may be

connected from the input to supply lines.

Copyright © 2002–2015, Texas Instruments Incorporated

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