INA333_3 datasheet(12/25 Pages) TI

12 / 25 page

NOISE PERFORMANCE

INTERNAL OFFSET CORRECTION

INPUT BIAS CURRENT RETURN PATH

OFFSET TRIMMING

10kW

OPA333

±10mV

AdjustmentRange

100W

100 A

1/2REF200

100 A

1/2REF200

V+

V-

INA333

Ref

IN-

IN+

INA333

SBOS445B – JULY 2008 – REVISED OCTOBER 2008 ..................................................................................................................................................... www.ti.com

Table 1. Commonly-Used Gains and Resistor Values

DESIRED GAIN

RG (Ω)

NEAREST 1% RG (Ω)

NC(1)

100k

25k

24.9k

11.1k

11k

5.26k

5.23k

2.04k

2.05

100

1.01k

200

502.5

499

500

200.4

200

1000

100.1

100

(1)

NC denotes no connection. When using the SPICE model, the simulation will not converge unless a resistor is connected to the RG pins;

use a very large resistor value.

The auto-calibration technique used by the INA333

The INA333 internal op amps use an auto-calibration

results in reduced low frequency noise, typically only

technique with a time-continuous 350kHz op amp in

50nV/

√Hz, (G = 100). The spectral noise density can

the signal path. The amplifier is zero-corrected every

be seen in detail in Figure 8. Low frequency noise of

µs using a proprietary technique. Upon power-up,

the INA333 is approximately 1

µV

PP measured from

the amplifier requires approximately 100

µs to achieve

0.1Hz to 10Hz, (G = 100).

specified VOS accuracy. This design has no aliasing

or flicker noise.

The input impedance of the INA333 is extremely

high—approximately 100G

Ω. However, a path must

Most

applications

require

external

offset

be provided for the input bias current of both inputs.

adjustment; however, if necessary, adjustments can

This input bias current is typically ±70pA. High input

be made by applying a voltage to the REF terminal.

impedance

means

that

this

input

bias

current

Figure 33 shows an optional circuit for trimming the

changes very little with varying input voltage.

output offset voltage. The voltage applied to REF

terminal is summed at the output. The op amp buffer

Input circuitry must provide a path for this input bias

provides low impedance at the REF terminal to

current for proper operation. Figure 34 illustrates

preserve good common-mode rejection.

various provisions for an input bias current path.

Without a bias current path, the inputs will float to a

potential that exceeds the common-mode range of

the INA333, and the input amplifiers will saturate. If

the differential source resistance is low, the bias

current return path can be connected to one input

(see the thermocouple example in Figure 34). With

higher source impedance, using two equal resistors

provides a balanced input with possible advantages

of lower input offset voltage as a result of bias current

and better high-frequency common-mode rejection.

Figure 33. Optional Trimming of Output Offset

Voltage

Submit Documentation Feedback

Product Folder Link(s): INA333

INA333 数据表(PDF) 12 Page - Texas Instruments

INA333 数据表(HTML) 12 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

数据表下载