Moteur de recherche de fiches techniques de composants électroniques
Selected language     French  ▼

Delete All
ON OFF
ALLDATASHEET.FR

X  

Preview PDF Download HTML

AD712AQ Datasheet(Fiches technique) 11 Page - Analog Devices

Numéro de pièce AD712AQ
Description  Dual Precision, Low Cost, High Speed BiFET Op Amp
Télécharger  20 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Fabricant  AD [Analog Devices]
Site Internet  http://www.analog.com
Logo AD - Analog Devices

AD712AQ Datasheet(HTML) 11 Page - Analog Devices

Back Button AD712AQ Datenblatt HTML 7Page - Analog Devices AD712AQ Datenblatt HTML 8Page - Analog Devices AD712AQ Datenblatt HTML 9Page - Analog Devices AD712AQ Datenblatt HTML 10Page - Analog Devices AD712AQ Datasheet HTML 11Page - Analog Devices AD712AQ Datenblatt HTML 12Page - Analog Devices AD712AQ Datenblatt HTML 13Page - Analog Devices AD712AQ Datenblatt HTML 14Page - Analog Devices AD712AQ Datenblatt HTML 15Page - Analog Devices Next Button
Zoom Inzoom in Zoom Outzoom out
 11 / 20 page
background image
AD712
Rev. G | Page 11 of 20
)
SETTLING TIME
OPTIMIZING SETTLING TIME
Most bipolar high speed digital-to-analog converters (DACs)
have current outputs; therefore, for most applications, an
external op amp is required for a current-to-voltage conversion.
The settling time of the converter/op amp combination depends
on the settling time of the DAC and output amplifier. A good
approximation is
() (
2
2
AMP
t
DAC
t
Total
t
S
S
S
+
=
The settling time of an op amp DAC buffer varies with the noise
gain of the circuit, the DAC output capacitance, and the amount
of external compensation capacitance across the DAC output
scaling resistor.
Settling time for a bipolar DAC is typically 100 ns to 500 ns.
Previously, conventional op amps have required much longer
settling times than have typical state-of-the-art DACs; therefore,
the amplifier settling time has been the major limitation to a
high speed, voltage output, digital-to-analog function. The
introduction of the AD71x family of op amps with their 1 ?s (to
0.01% of final value) settling time permits the full high speed
capabilities of most modern DACs to be realized.
In addition to a significant improvement in settling time, the
low offset voltage, low offset voltage drift, and high open-loop
gain of the AD71x family assure 12-bit accuracy over the full
operating temperature range.
The excellent high speed performance of the AD712 is shown in
the oscilloscope photos in Figure 30 and Figure 31. Measure-
ments were taken using a low input capacitance amplifier
connected directly to the summing junction of the AD712 and
both figures show a worst-case situation: full-scale input
transition. The 4 k? [10 k?||8 k? = 4.4 k?] output impedance
of the DAC, together with a 10 k? feedback resistor, produce an
op amp noise gain of 3.25. The current output from the DAC
produces a 10 V step at the op amp output (0 to ?10 V shown in
Figure 30, and ?10 V to 0 V shown in Figure 31).
Therefore, with an ideal op amp, settling to 1/2 LSB (0.01%)
requires that 375 ?V or less appears at the summing junction.
This means that the error between the input and output (that
voltage which appears at the AD712 summing junction) must
be less than 375 ?V. As shown in Figure 30, the total settling
time for the AD712/AD565A combination is 1.2 microseconds.
+15V
0.1F
0.1F
10pF
OUTPUT
?10V TO +10V
AD565A
?15V
IREF
BIPOLAR
OFFSET ADJUST
IO
0.1F
R1
100?
R2
100?
GAIN
ADJUST
REF
IN
REF
GND
?VEE
0.1F
POWER
GND
MSB
LSB
8k?
5k?
5k?
10V
19.95k?
0.5mA
DAC
OUT
10V
SPAN
20V
SPAN
VCC
REF
OUT
BIPOLAR
OFF
9.95k?
+
?
8
4
1/2
AD712
DAC
IOUT = 4
IREF CODE
20k?
Figure 29. 10 V Voltage Output Bipolar DAC


Html Pages

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


Datasheet Download

Go To PDF Page


Lien URL



Privacy Policy
ALLDATASHEET.FR
AllDATASHEET vous a-t-il été utile ?   [ DONATE ]  

propos de Alldatasheet   |   Publicit   |   Contactez-nous   |   Politique de confidentialit   |   Echange de liens   |   Manufacturer List
All Rights Reserved Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn