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unable to achieve gain using AD8003

Question asked by shyam.sunder91 on May 2, 2016
Latest reply on Jul 28, 2016 by harryh

before entering in to problem:

my application is a laser pulse detection, in this process when a laser pulse falls on photo diode it generates current, later stages include a I-V conversion, Gain,difference amplifier and comparator


my pulse characteristics:

pulse width min:10ns max:150ns rise/fall time:2ns-5ns pulse to pulse width:22uS


How i selected the opamp for Gain and difference amplifier stages

key parameters: BW - bandwidth and SR - Slew Rate

from this literature i found my BW can be calculated by formula

BW=0.35/(rise time)=0.35/5ns=70MHz

Now slew rate is to be calculated

SR = 2 * 3.14* BW * Vp = 2 * 3.14* 175MHz *4V = 2198V/us

So Matching both these parameters is a CFA AD8003 from Analog, when i go for high slew rates and high BW almost all opamps avaliable are CFA's !


here below is the desing as suggested in datasheet, pulse here is a 10ns pulse with 100ns repetetion and 1V amplitude fromt the voltage source, i used the TIs TINA simulation and imported the spice model given by Analog Devices



results are quite unexpected



Attachment is the design of the above circuit which can be opened and simulated using TINA, because i did not find AD8003 in analog simulator and i was not able to import the spice model to ADI simulator


Kindly help in taking the advantage of AD8003