Datenblatt-Suchmaschine für elektronische Bauteile
  German  ▼
ALLDATASHEETDE.COM

X  

AD648AQ Datenblatt(PDF) 10 Page - Analog Devices

Teilenummer AD648AQ
Bauteilbeschribung  Dual Precision, Low Power BiFET Op Amp
Download  12 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Hersteller  AD [Analog Devices]
Direct Link  http://www.analog.com
Logo AD - Analog Devices

AD648AQ Datenblatt(HTML) 10 Page - Analog Devices

Back Button AD648AQ Datasheet HTML 4Page - Analog Devices AD648AQ Datasheet HTML 5Page - Analog Devices AD648AQ Datasheet HTML 6Page - Analog Devices AD648AQ Datasheet HTML 7Page - Analog Devices AD648AQ Datasheet HTML 8Page - Analog Devices AD648AQ Datasheet HTML 9Page - Analog Devices AD648AQ Datasheet HTML 10Page - Analog Devices AD648AQ Datasheet HTML 11Page - Analog Devices AD648AQ Datasheet HTML 12Page - Analog Devices  
Zoom Inzoom in Zoom Outzoom out
 10 / 12 page
background image
AD648
REV. C
–10–
LOG RATIO AMPLIFIER
Log ratio amplifiers are useful for a variety of signal condition-
ing applications, such as linearizing exponential transducer out-
puts and compressing analog signals having a wide dynamic
range. The AD648’s picoamp level input current and low input
offset voltage make it a good choice for the front-end amplifier
of the log ratio circuit shown in Figure 30. This circuit produces
an output voltage equal to the log base 10 of the ratio of the in-
put currents I1 and I2. Resistive inputs R1 and R2 are provided
for voltage inputs.
Input currents I1 and I2 set the collector currents of Q1 and Q2,
a matched pair of logging transistors. Voltages at points A and B
are developed according to the following familiar diode equation:
VBE = (kT/q) ln (IC/IES)
In this equation, k is Boltzmann’s constant, T is absolute tem-
perature, q is an electron charge, and IES is the reverse satura-
tion current of the logging transistors. The difference of these
two voltages is taken by the subtractor section and scaled by a
factor of approximately 16 by resistors R9, R10 and R8. Tem-
perature compensation is provided by resistors R8 and R15,
which have a positive 3500 ppm/
°C temperature coefficient.
The transfer function for the output voltage is:
VOUT = 1 V log10 (I2/I1)
Frequency compensation is provided by R11, R12, C1, and C2.
Small signal bandwidth is approximately 300 kHz at input cur-
rents above 100
µA and will proportionally decrease with lower
signal levels. D1, D2, R13, and R14 compensate for the effects
of the two logging transistors’ ohmic emitter resistance.
To trim this circuit, set the two input currents to 10
µA and ad-
just VOUT to zero by adjusting the potentiometer on A3. Then
set I2 to 1
µA and adjust the scale factor such that the output
voltage is 1 V by trimming potentiometer R10. Offset adjust-
ment for A1 and A2 is provided to increase the accuracy of the
voltage inputs.
This circuit ensures a 1% log conformance error over an input
current range of 300 pA to l mA, with low level accuracy limited
by the AD648’s input current. The low level input voltage accu-
racy of this circuit is limited by the input offset voltage and drift
of the AD648.
Figure 30. Precision Log Ratio Amplifier


Ähnliche Teilenummer - AD648AQ

HerstellerTeilenummerDatenblattBauteilbeschribung
logo
Analog Devices
AD648 AD-AD648_15 Datasheet
209Kb / 12P
   Dual Precision, Low Power BiFET Op Amp
REV. E
More results

Ähnliche Beschreibung - AD648AQ

HerstellerTeilenummerDatenblattBauteilbeschribung
logo
Analog Devices
AD648 AD-AD648_15 Datasheet
209Kb / 12P
   Dual Precision, Low Power BiFET Op Amp
REV. E
AD548SH AD-AD548SH Datasheet
221Kb / 12P
   Precision, Low Power BiFET Op Amp
REV. D
AD548 AD-AD548 Datasheet
198Kb / 8P
   Precision, Low Power BiFET Op Amp
REV. B
AD548 AD-AD548_02 Datasheet
221Kb / 12P
   Precision, Low Power BiFET Op Amp
REV. D
AD548KNZ AD-AD548KNZ Datasheet
221Kb / 12P
   Precision, Low Power BiFET Op Amp
REV. D
AD548 AD-AD548_15 Datasheet
221Kb / 12P
   Precision, Low Power BiFET Op Amp
REV. D
AD642 AD-AD642 Datasheet
395Kb / 6P
   Precision, Low Cost Dual BiFET Op Amp
REV. 0
AD642 AD-AD642_15 Datasheet
399Kb / 6P
   Precision, Low Cost Dual BiFET Op Amp
REV. 0
AD712 AD-AD712_06 Datasheet
522Kb / 20P
   Dual Precision, Low Cost, High Speed BiFET Op Amp
Rev. G
AD712 AD-AD712 Datasheet
635Kb / 15P
   Dual Precision, Low Cost, High Speed, BiFET Op Amp
REV. B
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12


Datenblatt Download

Go To PDF Page


Link URL




Privatsphäre und Datenschutz
ALLDATASHEETDE.COM
War ALLDATASHEET hilfreich?  [ DONATE ] 

Über Alldatasheet   |   Werbung   |   Kontakt   |   Privatsphäre und Datenschutz   |   Linktausch   |   Hersteller
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