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High-Speed Current Amplifier for Signal Amplification

Jose Parodi
Prodigy 70 points
Other Parts Discussed in Thread: THS4631, LM359, THS6182, OPA2670, THS6132, THS6012, THS6002, OPA2673, OPA2677

Hi everyone,

I'm new to the TI forums so please bear with me in any lack of common forum knowledge/expertise.

I'm designing a high-speed, high-power signal amplifier and can't seem to find the power IC for my needs:

Operating Frequency: 100 kHz - 5 MHz
Output Current: 100 mA minimum, >500 mA ideal.
Vin is sinusoid.

Amount of sources and input voltage are 2 sources max, 10 V p-p max. Distortion levels should be low. Basically, I am trying to amplify the current coming from a function generator while maintaining good signal fidelity (low distortion).

Any advice/comments are welcome.

Best Regards,
Aquiles Parodi

  • 0
    Intellectual 310 points

    Hi Jose,

    Please check if THS4631 will match with your requirement.

    Regards,

    Binoy.

  • 0 in reply to Binoy Raphael
    Prodigy 70 points

    Hi Binoy,

    Thanks for the help.

    THS4631 matches my frequency response requirements, but I doubt it will be able to drive the load properly. I'm also looking at other products (like the LM359). I'm thinking I may have to implement a multi-stage amplifier, but the problem again is the maximum output current at high frequencies.


    Best,
    Aquiles Parodi

  • 0 in reply to Jose Parodi
    TI__Genius 15975 points

    Hi Jose,

    Few options to consider for your application would be THS6132, THS6182, THS6002, THS6012, OPA2670. There are quite a lot of options which you can also browse through in TI High Speed Amplifiers http://www.ti.com/lsds/ti/amplifiers-linear/high-speed-amplifier-greater-than-equal-50MHz-products.page product folder with parts in the range of 100mA to 700mA output current drive with your input frequency of interest by playing with the Io knob.

    What is the highest load that you are looking for your application? We can narrow down the search if there are any more specific requirements.

    Best Regards,

    Rohit

  • 0 in reply to Rohit Bhat
    TI__Genius 12631 points

    Hello Jose,

     You mentioned that you are trying to amplify the current from a function generator. What is the current range expected out from the function generator? Is the current going to be uni-polar or bipolar?

    Are you planning on using the opamp as a transimpedance amplifier or will you be dropping the current across a shunt resistor and then amplifying that voltage?

    With regards to the power supplies, do you have a restriction on the supply voltage or is it flexible to meet the circuit needs?

    Samir

  • 0 in reply to Samir Cherian
    Prodigy 70 points

    Hi Samir,

    Thanks for the reply. I think I worded the question improperly, since I am not trying to amplify a small current for sensing purposes, instead I am trying to amplify the current from a frequency generator to generate a strong magnetic field (at a specific frequency). I hope this clarifies.

    Regardless: Current range: 25 mA - 50 mA, bipolar.

    I don't think a transimpedance amplifier or the use of a shunt resistor apply in this case. I'm trying to get the current to flow through an inductor.

    The power supply is variable with a Vdcmax of 20V.

    Let me know what you think.


    Thanks,
    Aquiles Parodi

  • 0 in reply to Jose Parodi
    TI__Genius 15975 points

    Hi Jose,

    You mentioned in the post that you have 2 sources (I believe they are frequency generators) with each being able to output 10Vpp (max). May I know which frequency generator are you using for your application? Also, I wanted to clarify that the output coming from the frequency generator is a voltage of 10V(p-p) as the input to the amplifier or its a current of 25mA - 50mA?

    I am thinking either scenario you would want an output current drive of 500mA ideal into the inductor so as to generate a strong magnetic field at its resonant frequency. A transimpedance amplifier may not work in your application but converting current into voltage by using a shunt resistor might be beneficial so that the amplifier could provide the appropriate output current drive at the inductor's resonant frequency.

    Best Regards,

    Rohit

  • 0 in reply to Rohit Bhat
    TI__Genius 12631 points

    Hello Jose,

    Could you please provide a schematic with some illustrations so that we can better guide you.

    Thanks,

    Saimir.

  • 0 in reply to Rohit Bhat
    Prodigy 70 points

    Hello Rohit,

    The generator is a Hewlett-Packard 3325B (standard model). And you're right, a proper shunt resistor would work. Any best practices advice on current amplifiers for inductors would be appreciated.

    The output of the function generator is 10V(p-p).

    The amplifier that I think would work is the OPA2673, but in the sample/buy page it says "Contact TI", any information on how to proceed with this?

    Best Regards,

    Aquiles Parodi

  • 0 in reply to Jose Parodi
    TI__Genius 15975 points

    Hi Jose,

    It might be possible to sample/buy the OPA2673 from the authorized distributors mentioned in the TI website if you click on the "Buy from Distributor" tab right next to the "Contact TI". I think it might be possible for you to get free samples if you ask the distributor. You could also order the OPA2677 which is a similar but slightly lower performance part than the OPA2673, but I see free samples that you could order for the OPA2677 in SO Power PAD and SOIC 8-pin package. I would follow the recommendations mentioned in the Application Information of OPA2673 datasheet for best practices to design the circuitry around OPA2673. 

    Best Regards,

    Rohit