INA137UASLASH2K5 datasheet(8/15 Pages) TI2

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INA137, INA2137

The INA137 and INA2137 have excellent distortion charac-

teristics. THD+Noise is below 0.001% throughout the audio

frequency range. Up to approximately 10kHz distortion is

below the measurement limit of commonly used test equip-

ment. Furthermore, distortion remains relatively flat over its

wide output voltage swing range (approximately 1.7V from

either supply).

OFFSET VOLTAGE TRIM

The INA137 and INA2137 are laser trimmed for low offset

voltage and drift. Most applications require no external offset

adjustment. Figure 3 shows an optional circuit for trimming

the output offset voltage. The output is referred to the output

reference terminal (pin 1), which is normally grounded. A

voltage applied to the Ref terminal will be summed with the

output signal. This can be used to null offset voltage as

shown in Figure 3. The source impedance of a signal applied

to the Ref terminal should be less than 10

Ω to maintain good

common-mode rejection.

APPLICATIONS INFORMATION

The INA137 and INA2137 are differential line receivers

suitable for a wide range of audio and general-purpose

applications. Figure 1 shows the basic G = 1/2 (–6dB)

differential receiver configuration. The input and feedback

resistors can be reversed to achieve G = 2 (+6dB), as shown

in Figure 2. For applications requiring G = 1 (0dB), the

INA134 and INA2134 are recommended.

Decoupling capacitors are strongly recommended for appli-

cations with noisy or high impedance power supplies. The

capacitors should be placed close to the device pins as

shown in Figure 1. All circuitry is completely independent

in the dual version assuring lowest crosstalk and normal

behavior when one amplifier is overdriven or short-cir-

cuited.

As shown in Figure 1, the differential input signal is con-

nected to pins 2 and 3. The source impedances connected to

the inputs must be nearly equal to assure good common-

mode rejection. A 5

Ω mismatch in source impedance will

degrade the common-mode rejection of a typical device to

approximately 77dB (RTO). If the source has a known

impedance mismatch, an additional resistor in series with

the opposite input can be used to preserve good common-

mode rejection.

FIGURE 3. Offset Adjustment.

AUDIO PERFORMANCE

The INA137 and INA2137 were designed for enhanced ac

performance. Very low distortion, low noise, and wide band-

width provide superior performance in high quality audio

applications. Laser-trimmed matched resistors provide opti-

mum common-mode rejection (typically 90dB), especially

when compared to circuits implemented with an op amp

and discrete precision resistors. In addition, high slew rate

(14V/

µs) and fast settling time (3µs to 0.01%) ensure excel-

lent dynamic performance.

INA137

O = 1/2 (V3 – V2)

12k

Ω

12k

Ω

–In

+In

1µF

V–

1µF

V+

FIGURE 1. G = 1/2 Differential Receiver (Basic Power

Supply and Signal Connections).

INA137

O = 2 (V3 – V2)

Ω

12k

Ω

12k

Ω

–In

+In

FIGURE 2. G = 2 Differential Receiver.

INA137

O = 1/2 (V3 – V2)

Offset Adjustment

Range = ±1mV

G = 1/2

Ω

250k

Ω

100k

Ω

+15V

–15V

12k

Ω

12k

Ω

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