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OPA353: constant current source using OPA353_Frequency Response

HARI T O1
Expert 1395 points
Part Number: OPA353

Dear Team,

I am making a constant current source using OPA353.My circuit is given below. 

The frequency respose plot obtaned is also shown.

May I know is this respose expected.How to find the bandwidth of the complete circuit.

Regards

HARI

  • 0
    Guru 140200 points

    Hi Hari,

    looks like you violate the common mode input voltage range of OPAmp. Set the DC input voltage different from zero Volt. Try 1V.

    Can you post the TSC-file?

    Kai

  • 0 in reply to kai klaas69
    Expert 1395 points

    BUFFER_1.TSC

    Hi Kai..

    Please find the attached.

    Regards

    Hari

  • 0 in reply to HARI T O1
    Guru 140200 points

    Hi Hari,

    as I said the simu works with a DC input voltage of 1V:

    hari_opa353.TSC

    Though, from the peak in the frequency response and the overshot in the transient analysis it can be seen that the circuit is not very stable.

    Do you want support in increasing the stability of this circuit?

    Kai

  • 0 in reply to kai klaas69
    Expert 1395 points

    Hi Kai,

    Thank you very much.

    Definitely I need a support in increasing the stability of the circuit.

    Regards

    HARI

  • 0 in reply to HARI T O1
    TI__Mastermind 20382 points

    Hey Hari, 

    Have you seen this circuit? 

    High-side V-I with bipolar junction transistor (BJT) circuit

    Feedback components R3, R4, and C1 provide compensation to ensure stability. R3 isolates the input capacitance of the bipolar junction transistor (BJT), R4 provides a DC feedback path directly at the currentsetting resistor (R5), and C1 provides a high-frequency feedback path that bypasses the BJT.

    All the best,
    Carolina 

  • 0 in reply to HARI T O1
    Guru 140200 points

    Hi Hari,

    I tried to compensate the circuit as discussed in the link given by Caro. But because the OPA353 is so fast I was not able to find a proper phase lead compensation for this circuit.

    Do you really need to take the OPA353 in this circuit? What bandwidth do you need? And what is the load?

    It seems that the chosen OPAmp and NPN do not fit well together. Can you take another NPN?

    Please tell more about the application.

    Kai

  • 0 in reply to kai klaas69
    Expert 1395 points

    Hi Kai,

    OPA353 is already in my hand,that is why I went with it.

    I can purchase new opamp and BJT not an issue.

    My bandwidth is maximum 5Mhz.

    The load is our ASIC.

    Regards

    HARI

  • 0 in reply to HARI T O1
    Guru 140200 points

    Hi Hari,

    HARI T O1 said:
    The load is our ASIC.

    Do you know the load resistance? Is it a pure resistive load? Or is there any load capacitance and/or inductance?

    And I would like to know why you need an aditional NPN output stage. I ask because the OPA353 has a rather strong output stage and can sink and source up to 40mA.

    Kai

  • 0 in reply to kai klaas69
    Expert 1395 points

    Hi Kai,

    Regarding load resistance ,I will check with ASIC design team and let you know by tomorrow.

    They will be flashing some fuses inside the ASIC.During that time ASIC will take 100mA of current.

    Regards

    HARI