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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

GAIN_AD8003.JPG

 

results are quite unexpected

AD8003_GAIN.jpg

 

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

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