THS4631DDAEVM: Infrared detector amplifier

Hello JL,

    What is the voltage range at the output of the THS4631, and what is the desired output voltage range for the additional amplifier? Also, what will be the load at the output of the additional amplifier?

Thank you,

Sima

Dear Sima

The output voltage of the THS4631 for input signal from the photodiode is about 50 µV. The desired output voltage for the additional amplifier would be from 2 to 10 mV and output impedance 50 ohms since I work at high frequency (from 50 to 200 MHz).

What do you think about the THS4021 EVM ?

Thank you for helping

JL

Look at the OPA855, says it is a transimpedance amp but that is just an application, just use it as a voltage gain stage, 

Thank you Michael

You think it is better to replace the THS4631 with the OPA855 or to use the OPA at the outup of the THS ?

JL

Hello JL,

   Replacing it with the OPA85x family would be a better option based on the earlier replies. A higher gain bandwidth product could help in your case. What is the capacitance of your photodiode?

Thank you,

Sima

Hi JL,

yes, please give us a link to the datasheet of photodiode. And can you tell more about the photodiode's signal? Shape, rise time, fall time, repetition rate, etc.?

Kai

Hi,

Here are the data from the provide (Kolmar tech.) :

Detector data:                                                 Units

      Size:                          1                               mm DIA.
      Active area:            7.85E-03                               cm^2
      Responsivity(DETECTOR):     6.78                               Amp/Watt
      Quantum efficiency PEAK:    0.80 @ BIAS V     0.06             window included
      Peak wavelength:           10.53                               um
      Cut off wavelength:        11.45                               um
      Resistance (@V=0):           200                               Ohm
      RoA :                       1.57                               Ohm-cm^2
      BACK IMPEDANCE              3000    0.063 @ V                  Ohm
      R series                       5 max                           Ohm
      risetime                1.86E-07                               sec
      Bandwidth(-3db)                2 NOM                           MHz


Thanks for helping

Jean-Luc

Bon jour Jean-Luc,

can you please add the detector capacitance?

Kai

Hi Kai

In fact the capacitance is generally not given by the provider since it depends on the area of the element (1 mm square in the present) state. However , we measured that the risetime is about 35 nsec and the resistance is 180 ohms, then I would say that the capacitance is about 35e-9/180 = 0.2 nF.

Does it sound coferent to you ?

JL

Hi Jean-Luc,

the KLD series seems to contain a pre-amplifier:

I would try to contact the manufacturer for further details.

Kai