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100W Amplifier to Power 485 kHz sine wave

Kyle Statsman39
Prodigy 30 points

Hello,

I am wondering if anyone has any experience designing something in the IF range.  We are trying to develop an amplifier circuit that can power a 485 kHz sine wave through a 25-300 ohm load at 100 watts.

I was looking at the audio amplifiers and it seems that we would exceed their capable frequency and would exceed the typical speaker load.

Thanks,

Kyle

  • 0
    TI__Guru* 93105 points

    Hello Kyle,

    It is unlikely that there is an integrated circuit amplifier solution that will be able to provide the 100 Watt output power required for a 485 kHz application. You stated that the RL would have a range of 25 to 300 Ω. If we calculate the peak voltage associated with 100 WRMS and that resistance range:

    P = E2 / R,        E = (P∙R)0.5

    E1 = (100 ∙ 25)0.5 = 50 VRMS        E2 = (100 ∙ 300)0.5 = 173 VRMS

    E1PK = 1.414 (50) = 70.7 VPK      E2PK = 1.414 (173) = 245 VPK

    I1PK = E1PK / RL = 70.7 / 25 = 2.83 APK     I2PK = E2PK / RL = 245 / 300 = 0.82 APK

    The output voltage levels are quite high; the output current is high too. The supply voltage used to power the amplifier would have to be even higher unless a step-up transformer is used to step up a low-voltage, high-current output, up to a high-voltage, lower current output. None of our power op amps are able to meet the high voltage, or bandwidth requirements.

    There are solid-state RF power amplifiers that operate in the medium frequency (MF) range in which 485 kHz lies. It is completely possible to design and construct a discrete transistor (likely, power MOSFET) RF amplifier that will do what you need. You may want to do a search on line to see if, and how, others have approached a solution.

    Regards, Thomas

    Precision Amplifier Applications Engineering