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IVC102 Question(s)

Bonnie Baker - WEBENCH Design Center
Expert 3555 points
Other Parts Discussed in Thread: IVC102, DDC112

Hello Bonnie,

I read your articles in EDN all the time and have a few questions concerning the IVC102 Switched Integrator TIA.

Any information you could forward concerning the operation and noise analysis of this device would be helpful. 

My application is attempting to use this device with an unbiased InGaAs photodetector.

This configuration seems to offer the best noise performance at low signal levels (bias voltage induced dark current is gone).

Have you considered or worked with anyone using the device in this configuration?

The only draw back I can see is the output noise hit because of the higher input capacitance.

Here are my more general questions on the device;

The 10 nV/rt(Hz) noise voltage given on the data sheet… is it input referred or output?

The temperature performance of this device is not specified in the data sheet…can you offer any other sources to help in determining the performance of this device over temp?

I see a curve for the input bias current over temp…is this for both the inverting & non inverting nodes?  I’m also assuming this will induce a temperature dependent output voltage swing is this the case?

The device seems to be specified at +/-15V any thoughts on my trying +/-5V?

Again any insight you could offer would be greatly appreciated.

Robert.

  • 0
    TI__Expert 3555 points

    Hello Robert,

    I have not worked with anyone using an InGaAs photodetector, but if you can model this device as any photodiode you questions will apply to what I know. 

    You are right about the IVC noise relationship to higher input capacitances. Yes it will increase as the input capacitance increases. It is also true that if you increase the capacitor in the feedback loop of the amplifier the noise will decrease. The 10 nV/rt Hz is a noise figure that is referred to the input of the device. This is done so that you can calculate the nosie at the output of the IVC given your input and output capacitance.

    I am not sure about your request of more temperature performance specifications. As I reveiw the data sheet, I am seeing several specifications that refer to the temperature performance of this device. Could you give me a better idea about what you are specificallly looking for? Perhaps you are concerned about the typical specificaitons as opposed to minimums and maximums. At any rate, the input bias current over temperature that is given in the curves is for both of the ampliferi inputs, however you will not see hte effects of the non-inverting input because that is grounded. This specification is temperature dependent and the additional current from the inverter input will charge the feedback capacitor causing an error over temperature.

    As for the device power supply voltages, these specifications were vary carefully defined. The limitation of -10 V on the negative power supply is limited by the switched around the amplifer. The limitation of +4.75V on the positive power supply is set by the amplifier.  I would not recommend that you operate this device with +/- 5V supplies.

    Robert, thanks for you questions. if you have any more, please resond on this forum.

    Best Regards,

    Bonnie Baker

  • 0 in reply to Bonnie Baker - WEBENCH Design Center
    Prodigy 10 points

    Thanks for responding to my questions.  I have found additional references in the form of articles and applications notes you have published.  They have lead me to considering devices like the ddc112 ADC or as I refer to it charge to digital converter.  Can you offer any insight into what performance improvements I may see.  Also I am very concerned about powering this device or the ivc102 any pointers you can offer in providing the cleanest possible supplies?

     

    Again thanks for your help!