AD711KR Analog Devices Inc, AD711KR Datasheet - Page 10

• Manufacturer Part Number: AD711KR
• Description: IC OPAMP BIFET PREC 25MA 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD711KR

• Rohs Status: RoHS non-compliant
• Amplifier Type: J-FET
• Number Of Circuits: 1
• Slew Rate: 20 V/µs
• -3db Bandwidth: 4MHz
• Current - Input Bias: 15pA
• Voltage - Input Offset: 200µV
• Current - Supply: 2.5mA
• Current - Output / Channel: 25mA
• Voltage - Supply, Single/dual (±): 9 V ~ 36 V, ±4.5 V ~ 18 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Output Type: -
• Gain Bandwidth Product: -

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.
TRIM
RESISTOR JN/AQ/SD KN/BQ/TD LN/CQ/UD GLN/GCQ/GUD
R1
R2
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
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.
Table I. Recommended Trim Resistor Values vs. Grades
of the AD7545 for V
V
IN
* FOR VALUES R1 AND R2,
REFER TO TABLE 1
ADJUST
GAIN
R1 *
Figure 8. Unipolar Binary Operation
500 W
150 W
DB11-DB0
V
REF
V
V
DD
DD
DGND AGND
DD
R
AD7545
200 W
68 W
FB
= 5 V
* FOR VALUES R1 AND R2,
V
REFER TO TABLE 1
IN
OUT1
R2 *
COMMON
ANALOG
33pF
C1
ADJUST
GAIN
R1 *
100 W
33 W
AD711K
V
+15
–15
DGND
REF
V
V
DD
DD
0.1 F
0.1 F
AD7545
DATA INPUT
DB11-DB0
R
20 W
6.8 W
C
FB
12
F
Figure 9. Bipolar Operation
AGND
OUT1
R2 *
V
OUT
C1
33pF
ANALOG
COMMON
–10–
AD711K
+15V
–15V
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.
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
Figure 10. Settling Characteristics for AD711 with AD7545
ANALOG
0.1 F
0.1 F
a. Full-Scale Positive
Transition
INPUT
10V
Figure 11. AD711 as ADC Unity Gain Buffer
10k
20k
1%
R3
1%
R4
AD711
+15V
–15V
AD711K
+15V
–15V
20k
0.1 F
0.1 F
1%
R5
0.1 F
0.1 F
ANALOG COM
OFFSET
ADJUST
ADJUST
100
100
GAIN
R2
R1
V
OUT
b. Full-Scale Negative
Transition
12/8
CS
R/C
CE
REF IN
REF OUT
BIP OFF
10V
20V
ANA COM
A
O
IN
IN
AD574
DIG COM
MIDDLE
HIGH
+15V
–15V
BITS
BITS
LOW
BITS
STS
+5V
REV. E