INA133UASLASH2K5 datasheet(9/20 Pages) TI

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INA133, INA2133

APPLICATIONS INFORMATION

The INA133 and INA2133 are high-speed difference ampli-

fiers suitable for a wide range of general purpose applica-

tions. Figure 1 shows the basic connections required for

operation of the INA133. Decoupling capacitors are strongly

recommended 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 5

Ω mismatch in source impedance will

degrade the common-mode rejection of a typical device to

approximately 80dB (a 10

Ω mismatch degrades CMR to

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.

The INA133’s internal resistors are accurately ratio trimmed

to match. That is, R1 is trimmed to match R2 and R3 is

trimmed to match R4. However, the absolute values may not

be equal (R1 + R2 may be slightly different than R3 + R4).

Thus, large series resistors on the input (greater than 250

Ω),

even if well matched, will degrade common-mode rejection.

Circuit board layout constraints might suggest possible varia-

tions in connections of the internal resistors. For instance, it

appears that pins 1 and 3 could be interchanged. However,

because of the ratio trimming technique used (see paragraph

above) CMRR will be degraded. If pins 1 and 3 are inter-

changed, pins 2 and 5 must also be interchanged to maintain

proper ratio matching.

OPERATING VOLTAGE

The INA133 and INA2133 operate from single (+4.5V to

+36V) or dual (

±2.25V to ±18V) supplies with excellent

performance. Specifications are production tested with

±5V

and

±15V supplies. Most behavior remains unchanged

throughout the full operating voltage range. Parameters which

vary significantly with operating voltage are shown in the

Typical Performance Curves.

INPUT VOLTAGE

The INA133 and INA2133 can accurately measure differen-

tial signals that are above and below the supply rails. Linear

common-mode range extends from 2 • (V+)–3V to 2 • (V–)

+3V (nearly twice the supplies). See the typical performance

curve, “Input Common-Mode Voltage vs Output Voltage.”

OFFSET VOLTAGE TRIM

The INA133 and INA2133 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.

INA133

OUT = V3 – V2

Gain Error =

±0.01%

CMR = 90dB

Nonlinearity =

±0.0001%

25k

Ω

25k

Ω

25k

Ω

25k

Ω

–In

+In

µF

V–

µF

V+

FIGURE 1. Precision Difference Amplifier (Basic Power

Supply and Signal Connections).

INA133

O = V3 – V2

Offset Adjustment

Range =

±1mV

Ω

150k

Ω

100k

Ω

+15V

–15V

FIGURE 2. Offset Adjustment.

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