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Require pointers for a 300 Watts Linear amplifier with 500KHz Power Bandwidth

Sougata Das
Prodigy 60 points
Other Parts Discussed in Thread: OPA549

Hi All,

Forgive me if I am posting to a wrong forum. Moderators please move if required.

I need to figure out a low cost DIY solution for soft ferrite power loss testing. Below is what I have in mind:

  1. A toaster converted into a temperature controlled oven - I don't know what will be the max temp possible -- with thermocouple connected to the Raspberry Pi via ADC
  2. A Function Generator using Raspberry Pi+DDS Chip
  3. A Linear Power Amplifier with about 300 watts output power upto 500Khz
  4. VAW measurement via True RMS High Frequency Current and Voltage Transducer -> I2C for Raspberry Pi-( Yet to Figure Out )

I am clueless on the Linear power amp. Input will be a single frequency at a time, sweeping from low to high. However the load is completely inductive.  Class-A  with a tracking DC-DC (sort'a not envelope tracking, since input magnitude is fixed) converter to keep efficiency High (read Thermal Loss Low) is what I was pondering upon. But then I am not experienced in this subject. I am also concerned about VSWR protection for the amplifier output.

I can handle the programming jobs but I need reference for the amplifier part.

So my questions for the amplifier are:

  1. Homebrew 10KHz to 500KHz, 200 - 300 watts possible ? Being only experienced in embedded system and power electronics am I inviting nightmares ?
  2. Any circuit references ? Can I use Audio amplifier class AB as a starting point. Do I risk oscillating tweaking the compensation.
  3. Can a Power OP-AMP like the OPA549 be used at all with some boosting or paralleling ? Since the load and the input signal is constant once setup for each measurement cycle and the OP-AMP supports current programming, can I use a MSP430 to sense and balance currents between parallel units actively
  4. If yes with a GBW of 0.9MHz would it handle 500KHz LINEARLY ? What about the very low impedance inductive load. 

Consider me a newbie on amplifiers and ambitious too.

For the entire project and specifically the amplifier please comment, suggest, criticize scare, and enlighten me.

Regards

Sougata

P.S.: For those who are pondering why I am upto this: I will lose $200 on bet if I don't do this and risk losing 10 times if I try and fail.  

 

  • 0
    TI__Genius 12631 points

    Hello,

       What power supply rails are you planning on using? With the 200-300Watts of power what load current do you need and how much swing is on the output of the amp. Also, whats the gain you are planning on using the amplifier in? How much load are you planning on driving.

      While the OPA549 does have 0.9MHz Bandwidth, that is for small signals. If you are looking at large signal swings then the Slew Rate (SR) is important. There is a relationship between SR and Large Signal BW (LSBW).

    SR (in V/us) = 2*pi*Frequency(in MHz)*Amplitude of Sine (in volts)

    So for a 0.5MHz, 50V signal, you will require a SR of 157V/us. The OPA549 has much lower SR (9V/us), so this will not work for your application. All these numbers will get worse when driving heavy loads. You can use TINA spice to simulate your circuits and verify performance.

    I will see if someone from the Audio Amplifier group has any suggestions.

    Thanks,
    Samir

     

  • 0 in reply to Samir Cherian
    Prodigy 60 points

    Hi,

    Thanks Samir for the explanation on LSBW vs Slew Rate.

    I am looking forward to design suggestions from other people. I have posted in another forum outside ti and awaiting feedback.

    Regards

    Sougata