I am designing a TAI using this tool from Analog devices. The circuit and it's frequency response obtained from the design tool is given below.

Circuit Diagram:


Frequency Response


I simulated the same circuit in LTspice the only change I made is instead of dual supply I used single supply.I did not considered photodiode capacitance here.I will be biasing the photodiode as as shown in the first image.

In my circuit I am getting a bandwidth of only 10Hz!!!. Please find my simulation results below.The simulation file is also attached here.

May I know where I went wrong.

 

When you switch to single supply operation it is customary to adjust your reference point to 1/2 of Vcc and ensure that the input(s) remain within the range [0, Vcc]

 

I tried that also but no change in the bandwidth

 

Check your capacitor - 371 FARAD?

 

No that is femto farad not farad

 

I tried that also but no change in the bandwidth

It is not supposed to change the bandwidth. It is supposed to avoid saturating the output or going into non-linear behavior for an input approaching the rails. You must not have been paying attention when that feature was being discussed.

 

No that is femto farad not farad

Good luck finding one of those. You just might have to fabricate that one.

 

hi hoy,
As suggested, check the 371f.
Also check the settings for the simulation, What does 'M' mean???
E

 

I just simulated this circuit I obtained from Analog devices.Feedback resistor is 1 Megha Ohm.I know femto I won't get.
But Why I am not getting the bandwidth which AD tool is getting

 

hi hoy,
What BW do you see in the TI bandwidth calculator.?
E

 

Almost 500Khz

 

hi hoy,
This is what I see, using a stepped Cp value.
E

 

Hi Eric,
This looks good.
I believe the value of Cf{Cp} provided by the tool (https://tools.analog.com/en/photodiode/) is wrong