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trans impedance amplifiers

ganesh shaga
Prodigy 15 points
Other Parts Discussed in Thread: THS4631

Dear Sir,

              i have used THS4631 op amp as trans impedance amplifier in photo diode application.

i have tested it externally with REF 200 (current source ) 100uA with gain of 10 .

i have not connected load at op amp o/p.

without any input , in floating condition i am getting 2v output.by connecting reference source  it comes down to .2v.

op amp is heating what is the cause.

  • 0
    TI__Genius 12631 points

    The stability of the TIA configuration will depend on the value of feedback resistance, feedback capacitance and input capacitance (amplifier input capacitance + capacitance of the photodiode). From figure 2 of the datasheet of the THS4631,it looks like there is 3dB of peaking when no additional capacitance is added at the inputs of the THS4631. This indicates that the amplifier is marginally stable with no additional cap. You will need to do your analysisand testing for stability in the presence of that extra capacitance. Please see attached application note that describes how to stabilize a TIA.

    -Samir

    http://www.ti.com/lit/an/sboa122/sboa122.pdf