8

®

INA134/2134

APPLICATIONS INFORMATION

Figure 1 shows the basic connections required for operation

of the INA134. Decoupling capacitors are strongly recom-

mended in applications 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-circuited.

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 10

Ω mismatch in source impedance will

degrade the common-mode rejection of a typical device to

approximately 74dB. 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.

Do not interchange pins 1 and 3 or pins 2 and 5, even though

nominal resistor values are equal. These resistors are laser

trimmed for precise resistor ratios to achieve accurate gain

and highest CMR. Interchanging these pins would not pro-

vide specified performance.

AUDIO PERFORMANCE

The INA134 and INA2134 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 good

dynamic performance.

The INA134 and INA2134 have excellent distortion charac-

teristics. THD+Noise is below 0.002% 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 INA134 and INA2134 are laser trimmed for low offset

voltage and drift. Most applications require no external offset

adjustment. Figure 2 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 2. The source impedance of a signal applied

to the Ref terminal should be less than 10

Ω to maintain good

common-mode rejection.

V

3

5

6

1

3

INA134

V

2

R

3

25k

Ω

R

4

25k

Ω

R

1

25k

Ω

R

2

25k

Ω

V

2

–In

+In

1µF

V–

4

1µF

V+

7

FIGURE 1. Precision Difference Amplifier (Basic Power

Supply and Signal Connections).

FIGURE 2. Offset Adjustment.

V

3

5

6

3

V

O

INA134

V

Offset Adjustment

Range = ±300µV

2

R

3

R

1

R

2

R

4

V

2

10

Ω

499k

Ω

10

Ω

100k

Ω

+15V

–15V

1