guidance on the circuit analysis

Low Noise Single Supply Photodiode Amplifier

I am trying to understand the circuit shown above, with one JFET transistor at left side acting a current buffer and right hand side with a op amp.

this is a low noise transimpedance circuit,  which I think I can use or modified this circuit and used in my design, sensitive to noise and a current signal needed to be amplified to voltage signal in the end. 

the problem is that I am not quit sure how to analyse the circuit, should I use small-signal analysis? Do I need to derive the transfer function? 

why the Bandwidth is 2MHZ and where is the cut off frequency? and is the system stable or not? 

Can someone give me a clue or answer, please? 

Thanks

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  • 0
    •  Analog Employees 
    on Oct 27, 2016 6:07 PM

    To test out your circuit I would recommend you use circuit simulation software like some version of SPICE. If you are looking at the circuit you show which uses an LTC amplifier, LTSpice would be the best choice. If you are going to be replacing the amplifier with a low noise op-amp from Analog Devices you should use ADIsimPE. Free down load available here:

    ADIsimPE powered by SIMetrix/SIMPLIS | Design Center | Analog Devices 

    You can use an ideal AC current source to inject a small signal current at the input and sweep the frequency to obtain the response of the overall circuit. The AC sweep can also do noise analysis. You can also run a transient analysis to measure things like step response or any other large signal tests.

    Doug

Reply
  • 0
    •  Analog Employees 
    on Oct 27, 2016 6:07 PM

    To test out your circuit I would recommend you use circuit simulation software like some version of SPICE. If you are looking at the circuit you show which uses an LTC amplifier, LTSpice would be the best choice. If you are going to be replacing the amplifier with a low noise op-amp from Analog Devices you should use ADIsimPE. Free down load available here:

    ADIsimPE powered by SIMetrix/SIMPLIS | Design Center | Analog Devices 

    You can use an ideal AC current source to inject a small signal current at the input and sweep the frequency to obtain the response of the overall circuit. The AC sweep can also do noise analysis. You can also run a transient analysis to measure things like step response or any other large signal tests.

    Doug

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