Moteur de recherche de fiches techniques de composants électroniques
  French  ▼
ALLDATASHEET.FR

X  

AD515AK Fiches technique(PDF) 5 Page - Analog Devices

No de pièce AD515AK
Description  Monolithic Precision, Low Power FET-Input Electrometer Op Amp
Download  6 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricant  AD [Analog Devices]
Site Internet  http://www.analog.com
Logo AD - Analog Devices

AD515AK Fiches technique(HTML) 5 Page - Analog Devices

  AD515AK Datasheet HTML 1Page - Analog Devices AD515AK Datasheet HTML 2Page - Analog Devices AD515AK Datasheet HTML 3Page - Analog Devices AD515AK Datasheet HTML 4Page - Analog Devices AD515AK Datasheet HTML 5Page - Analog Devices AD515AK Datasheet HTML 6Page - Analog Devices  
Zoom Inzoom in Zoom Outzoom out
 5 / 6 page
background image
AD515A
–5–
REV. A
ELECTROMETER APPLICATION NOTES
The AD515A offers subpicoampere input bias currents available
in an integrated circuit package. This design will open up many
new application opportunities for measurements from very high
impedance and very low current sources. Performing accurate
measurements of this sort requires careful attention to detail;
the notes given here will aid the user in realizing the full
measurement potential of the AD515A and perhaps extending
its performance limits.
1. As with all junction FET input devices, the temperature of
the FETs themselves is critical in determining the input bias
currents. Over the operating temperature range, the input
bias currents closely follow a characteristic of doubling every
10
°C; therefore, every effort should be made to minimize
device operating temperature.
2. The heat dissipation can be reduced initially by careful
investigation of the application. First, if it is possible to
reduce the required power supplies, this should be done
since internal power consumption contributes the largest
component of self-heating. To minimize this effect, the
quiescent current of the AD515A has been reduced to less
than 1 mA. Figure 8 shows typical input bias current and
quiescent current versus supply voltage.
3. Output loading effects, which are normally ignored, can
cause a significant increase in chip temperature and therefore
bias current. For example, a 2 k
Ω load driven at 10 V at the
output will cause at least an additional 25 mW dissipation in
the output stage (and some in other stages) over the typical
24 mW, thereby at least doubling the effects of self-heating.
The results of this form of additional power dissipation are
demonstrated in Figure 9, which shows normalized input
bias current versus additional power dissipated. Therefore,
although many dc performance parameters are specified
driving a 2 k
Ω load, to reduce this additional dissipation, we
recommend restricting the load resistance to be at least 10 k
Ω.
4. Figure 10 shows the AD515A’s input current versus differen-
tial input voltage. Input current at either terminal stays below
a few hundred fA until one input terminal is forced higher
than 1 V to 1.5 V above the other terminal. Input current
limits at 30
µA under these conditions.
Figure 8. Input Bias Current and Supply Current vs.
Supply Voltage
Figure 9. Input Bias Current vs. Additional Power
Dissipation
Figure 10. Input Bias Current vs. Differential Input Voltage
AD515A CIRCUIT APPLICATION NOTES
The AD515A is quite simple to apply to a wide variety of
applications because of the pretrimmed offset voltage and
internal compensation, which minimize required external
components and eliminate the need for adjustments to the
device itself. The major considerations in applying this device
are the external problems of layout and heat control which have
already been discussed. In circuit situations employing the use of
very high value resistors, such as low level current to voltage
converters, electrometer operational amplifiers can be destabi-
lized by a pole created by the small capacitance at the negative
input. If this occurs, a capacitor of 2 pF to 5 pF in parallel with
the resistor will stabilize the loop. A much larger capacitor may
be used if desired to limit bandwidth and thereby reduce wide-
band noise.
Selection of passive components employed in high impedance
film or deposited ceramic oxide to obtain the best in low noise
and high stability performance. The best packaging for high
M
Ω resistors is a glass body sprayed with silicone varnish to
minimize humidity effects. These resistors must be handled
very carefully to prevent surface contamination. Capacitors for
any high impedance or long-term integration situation should
be of a polystyrene formulation for optimum performance.
Most other types have too low an insulation resistance, or high
dielectric absorption.
Unlike situations involving standard operational amplifiers with
much higher bias currents, balancing the impedances seen at
the input terminals of the AD515A is usually unnecessary and
probably undesirable. At the large source impedances, where
these effects matter, obtaining quality matched resistors will be
difficult. More important, instead of a cancelling effect, as with
bias current, the noise voltage of the additional resistor will add
by root-sum-of-squares to that of the other resistor thus increasing


Numéro de pièce similaire - AD515AK

FabricantNo de pièceFiches techniqueDescription
logo
Analog Devices
AD515A AD-AD515A_15 Datasheet
212Kb / 6P
   Monolithic Precision, Low Power FET-Input Electrometer Op Amp
REV. A
More results

Description similaire - AD515AK

FabricantNo de pièceFiches techniqueDescription
logo
Analog Devices
AD515A AD-AD515A_15 Datasheet
212Kb / 6P
   Monolithic Precision, Low Power FET-Input Electrometer Op Amp
REV. A
AD545A AD-AD545A Datasheet
280Kb / 4P
   Monolithic Precision, Low Drift FET-Input Op Amp
AD795 AD-AD795_02 Datasheet
278Kb / 16P
   Low Power, Low Noise Precision FET Op Amp
REV. B
AD795 AD-AD795_15 Datasheet
276Kb / 20P
   Low Power, Low Noise Precision FET Op Amp
REV. C
AD795 AD-AD795 Datasheet
331Kb / 16P
   Low Power, Low Noise Precision FET Op Amp
REV. A
AD795 AD-AD795_09 Datasheet
276Kb / 20P
   Low Power, Low Noise Precision FET Op Amp
REV. C
logo
Linear Technology
LT1792 LINER-LT1792 Datasheet
169Kb / 12P
   Low Noise, Precision, JFET Input Op Amp
LT1792 LINER-LT1792_15 Datasheet
184Kb / 12P
   Low Noise, Precision, JFET Input Op Amp
logo
M.S. Kennedy Corporatio...
MSK032 MSK-MSK032 Datasheet
181Kb / 5P
   FET INPUT DIFFERENTIAL OP-AMP
logo
Anaren Microwave
MSK032 ANAREN-MSK032 Datasheet
378Kb / 5P
   FET INPUT DIFFERENTIAL OP-AMP
More results


Html Pages

1 2 3 4 5 6


Fiches technique Télécharger

Go To PDF Page


Lien URL




Politique de confidentialité
ALLDATASHEET.FR
ALLDATASHEET vous a-t-il été utile ?  [ DONATE ] 

À propos de Alldatasheet   |   Publicité   |   Contactez-nous   |   Politique de confidentialité   |   Echange de liens   |   Fabricants
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
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com