How does Load Line of Class-F look like?

Discussion in 'General Electronics Chat' started by dMoser, Dec 11, 2011.

  1. dMoser

    Thread Starter Member

    Aug 25, 2011
    30
    1
    Hi,

    I'm studying the Class-F amplifier in order to eventually design one.
    I'm trying to figure out how a load like of a Class-F looks like, but didn't manage to find some clear information about it.

    I'd appreciate your help :)

    Thanks.
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. dMoser

    Thread Starter Member

    Aug 25, 2011
    30
    1
    Hi Bertus,
    The PDF is very informative and helped me, thank you :)

    I have a question please.
    Is it correct to say that the BIAS (VGS) of a Class F Amplifier is VTH (Threshold Voltage)?
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    In Class C E and F, the bias is below the threshold voltage.
    If the input signal gets high enough the output will show a pulse corresponding with the top of the input signal.

    Bertus
     
  5. dMoser

    Thread Starter Member

    Aug 25, 2011
    30
    1
    Thank you :)

    Are you sure regarding that?

    I read here (Page 34):
    "
    The quiescent point of Class F amplifiers must be close to the cutoff region in order to generate significant amount of harmonics.
    The class F bias is located a bit higher than that of Class B.
    The bias points for different PA classes are shown in Fig. 18.
    Because of their similar bias points, the drain waveforms of Class F are similar to those of Class B. With harmonic control, larger voltage is created in Class F with the current clipping at the same level as Class B.
    Therefore, Class F amplifiers are also known as overdriven Class B amplifier. Fig. 19 shows the voltage and current waveform of overdriven Class B PA, whose top of voltage waveform is flattened out as that in class F PA.​
    "
    http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1390&context=theses&sei-redir=1&referer=http%3A%2F%2Fwww.google.co.il%2Furl%3Fsa%3Dt%26rct%3Dj%26q%3Dclass%2520f%2520bias%2520point%26source%3Dweb%26cd%3D3%26ved%3D0CCwQFjAC%26url%3Dhttp%253A%252F%252Fdigitalcommons.calpoly.edu%252Fcgi%252Fviewcontent.cgi%253Farticle%253D1390%2526context%253Dtheses%26ei%3D5L_kToPoKJCgOrrs-c0E%26usg%3DAFQjCNEILRwHSc-4kWrAcG4YF3oxnlmp5g%26sig2%3DtV9PXH5Xh7_PZbRG2-dhvA#search=%22class%20f%20bias%20point%22
     
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