Can someone help me with this please

Discussion in 'Electronics Resources' started by zero_coke, Jan 30, 2013.

  1. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
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    DATASHEET LINK

    This power amplifier requires only a +30V signal at 5A, however, what I get on the output will also be a 0 to +30V signal? So technically, this is not an AC signal that is like -15 to +15 V but 0 - 30 V ??
     
  2. w2aew

    Member

    Jan 3, 2012
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    According to the data sheet, the amp will produce 60w of RF power, which is about 55Vrms. The fact that this amp is powered from a 30V DC supply really has no bearing on the RF output.
     
  3. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
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    Ok so I can assume my output will be a AC sinusoid and not an AC sinusoid that is offset in the >0 V region where it would then just be a DC signal with a big ripple right?
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,647
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    Hello,

    Did you ever look at the construction of RF amplifiers?
    At work we use RF power amplifiers that use 28 Volts DC and give out 300 Vpp RF signal.
    This is done with the use of RF transformers.
    Take a look at the attached PDF for some more info.

    Bertus
     
    Last edited: Jan 31, 2013
  5. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
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    So Bertus, does a unipolar DC source applied to such power amplifiers provide a - to + sine wave at the output ? I don't understand , I took a look at the pdf but I didn't find it.
     
  6. Papabravo

    Expert

    Feb 24, 2006
    10,140
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    Actually it does. The one thing we know for certain sure is that the power output will always be less than the power input. To get 60 watts of RF power out of a 30VDC supply will require at least 2 Amperes assuming 100% efficiency. If we assume say 80% efficiency then 60 watts output will require 75 watts input or 2.5 Amperes @ 30VDC.

    You are correct in stating that the number 30VDC all by itself is essentially meaningless except as it relates to the required current to provide the requisite input power.
     
  7. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
    294
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    Ok so here's my situation:

    I have a weak AC signal @ 10 MHz passing through this amplifier. This amplifier wants +30V @ 10 A to deliver 140W at the output. That's all the specs I get for it. Now, my confusion is, my weak signal is an AC signal meaning it goes below and beyond 0V obviously. My question is, at the output end, since the DC supply is only +30 and not +/-30V, does this mean I will be getting an AC-like waveform at the output that only exists above the 0V plane?

    I just don't see how only +30V DC can amplify my small signal's +5 and -5V peaks to +30 and -30V when the supply is only +30V. In the power amplifiers that we designed in class, they always had a + and - DC supply but these amplifiers that im looking at which are off-the-shelf only specify to use +30V only.
     
  8. Papabravo

    Expert

    Feb 24, 2006
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    zero_coke likes this.
  9. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
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  10. Papabravo

    Expert

    Feb 24, 2006
    10,140
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    Google and Wikipedia are good friends who should be visited often. Some people think "lmgtfy" is a snide suggestion, but I'm amazed at how many people it has helped. Glad that you are a satisfied customer.
     
  11. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
    294
    1
    Yeah the problem in my case is I didn't know what to google or I would've done it prior to submitting a thread. Sigh, a simple capacitor solved my problems! I had no idea lol...Oh well, need to think clearly next time!

    Thanks again!
     
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