INA143UASLASH2K5 datasheet(9/22 Pages) TI2

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INA143, INA2143

APPLICATIONS INFORMATION

The INA143 and INA2143 are high-speed difference ampli-

fiers suitable for a wide range of general-purpose applica-

tions. Figure 1 shows the basic G = 10 configuration. The

input and feedback resistors can be reversed to achieve

G = 0.1, as shown in Figure 2. For applications requiring

G = 1, the INA133 and INA2133 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 86dB (RTI). 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 INA143’s internal resistors are accurately ratio trimmed

to match. That is, R1/R2 and R3/R4 are trimmed to equal 0.1.

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 100

Ω), even if well matched, will

degrade common-mode rejection.

INA143

O = 10 (V3 – V2)

10k

Ω

100k

Ω

10k

Ω

100k

Ω

–In

+In

µF

V–

µF

V+

FIGURE 1. G = 10 Basic Power Supply and Signal Connections.

OPERATING VOLTAGE

The INA143 and INA2143 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.

OFFSET VOLTAGE TRIM

The INA143 and INA2143 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.

INA143

O = 0.1 (V3 – V2)

100k

Ω

10k

Ω

100k

Ω

10k

Ω

–In

+In

FIGURE 2. G = 0.1 Difference Amplifier.

FIGURE 3. Offset Adjustment.

INA143

O = 10 (V3 – V2)

Offset Adjustment

Range =

±3mV

Compensates

for impedance at

pin 1—see text.

G = 10

100k

Ω

499k

Ω

100

Ω

100k

Ω

+15V

–15V

10k

Ω

10k

Ω

100k

Ω

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