AD711KN 데이터 시트보기 (PDF) - Analog Devices

부품명

상세내역

제조사

AD711KN

Precision, Low Cost, High Speed, BiFET Op Amp

Analog Devices 

AD711

Figures 8 and 9 show the AD711 and AD7545 (12-bit CMOS

DAC) configured for unipolar binary (2-quadrant multiplication)

or bipolar (4-quadrant multiplication) operation. Capacitor C1

provides phase compensation to reduce overshoot and ringing.

R2*

GAIN

ADJUST

VIN

R1*

VDD

C1

33pF

VDD RFB OUT1

VREF AD7545

DGND AGND

DB11-DB0

*FOR VALUES R1 AND R2,

REFER TO TABLE 1

ANALOG

COMMON

+15

0.1␮F

AD711K

CF

0.1␮F

–15

VOUT

Figure 8. Unipolar Binary Operation

R1 and R2 calibrate the zero offset and gain error of the DAC.

Specific values for these resistors depend upon the grade of

AD7545 and are shown below.

Table I. Recommended Trim Resistor Values vs. Grades

of the AD7545 for VDD = 5 V

TRIM

RESISTOR JN/AQ/SD KN/BQ/TD LN/CQ/UD GLN/GCQ/GUD

R1

500 W 200 W

100 W

20 W

R2

150 W 68 W

33 W

6.8 W

compared to a series of switched trial currents. The comparison

point is diode clamped but may deviate several hundred millivolts

resulting in high frequency modulation of A/D input current.

Figures 10a and 10b show the settling time characteristics of the

AD711 when used as a DAC output buffer for the AD7545.

a. Full-Scale Positive

Transition

b. Full-Scale Negative

Transition

Figure 10. Settling Characteristics for AD711 with AD7545

compared to a series of switched trial currents. The comparison

point is diode clamped but may deviate several hundred milli-

volts resulting in high frequency modulation of A/D input

current. The output impedance of a feedback amplifier is made

artificially low by the loop gain. At high frequencies, where the

loop gain is low, the amplifier output impedance can approach

its open loop value. Most IC amplifiers exhibit a minimum open

loop output impedance of 25 W due to current limiting resistors.

A few hundred microamps reflected from the change in con-

verter loading can introduce errors in instantaneous input

NOISE CHARACTERISTICS

The random nature of noise, particularly in the 1/f region, makes

it difficult to specify in practical terms. At the same time,

designers of precision instrumentation require certain guaranteed

maximum noise levels to realize the full accuracy of their equipment.

The AD711C grade is specified at a maximum level of 4.0 mV p-p,

in a 0.1 Hz to 10 Hz bandwidth. Each AD711C receives a 100%

noise test for two 10-second intervals; devices with any excursion

in excess of 4.0 mV are rejected. The screened lot is then submitted

to Quality Control for verification on an AQL basis.

All other grades of the AD711 are sample-tested on an AQL

basis to a limit of 6 mV p-p, 0.1 to 10 Hz.

DRIVING THE ANALOG INPUT OF AN A/D CONVERTER

An op amp driving the analog input of an A/D converter, such

as that shown in Figure 11, must be capable of maintaining a

constant output voltage under dynamically changing load conditions.

In successive-approximation converters, the input current is

؎10V

ANALOG

INPUT

+15V

0.1␮F

AD711

0.1␮F

GAIN

ADJUST

R2

100⍀

R1

100⍀

OFFSET

ADJUST

12/8

STS

CS

HIGH

AO

BITS

R/C AD574

MIDDLE

CE

BITS

REF IN

REF OUT

LOW

BITS

BIP OFF

10VIN

20VIN

ANA COM

+5V

+15V

–15V

DIG COM

–15V

ANALOG COM

Figure 11. AD711 as ADC Unity Gain Buffer

VDD

R2*

GAIN

ADJUST

VDD RFB OUT1

VIN

R1*

VREF AD7545

AGND

DGND DB11-DB0

+15V

C1

0.1␮F

33pF

AD711K

0.1␮F

R4

20k⍀

1%

R3

10k⍀

1%

12

*FOR VALUES R1 AND R2, DATA INPUT

REFER TO TABLE 1

–15V

ANALOG

COMMON

Figure 9. Bipolar Operation

–10–

R5

20k⍀

1%

+15V

0.1␮F

AD711K

0.1␮F

–15V

VOUT

REV. E

Share Link: