We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissible in your locale.

Author Topic: Amplifier Topologies and Classes  (Read 2135 times)

Offline JimIO

  • Sr. Member
  • ****
  • Posts: 491
  • QTH I.O. MA
    • View Profile
Amplifier Topologies and Classes
« on: February 11, 2018, 2017 UTC »
Say I wanted to build an amp for 4 to 7 Mhz no tuning. Should I choose Single Ended or Push Pull. I know what and why for audio.

Offline digitalmod

  • Hero Member
  • *****
  • Posts: 572
  • Cherokee Foot Hills, SC
  • Freedom includes Radio Broadcasting
    • View Profile
    • Email
Re: Amplifier Topologies and Classes
« Reply #1 on: February 11, 2018, 2229 UTC »
 :) Mate, I am an engineer retired, wondering this myself. If you go single FET (YES its very doable) you have less peripheral toroids et-al. You will more than likely spend 10 USA dollars for a FET. It will in all likelihood need more power to drive than a modest push pull arrangement. The FET will not like much less than 50 volts Drain voltage as a single ended. Also the famous push and pull centered taped output network, reduces second harmonic way down. However, that said Fourier mathematics says a square wave (you won't see a perfect one) is ODD harmonics. In a way when you do a LPfilter having images at odd harminics gives you a LOWER Q. Well, that's as much take as I have at this point, but if I make it past my next car payment, I'll have a scope and a little lab before end of year. BTW not to worry mate, 48 volt switching supplies are cheap and easily available,
Radio is dying. We need to give it shelter

Offline Stretchyman

  • Hero Member
  • *****
  • Posts: 656
    • View Profile
Re: Amplifier Topologies and Classes
« Reply #2 on: February 12, 2018, 0746 UTC »
More 'Detail' needed!

PSU available, form factor, power O/P required etc etc.

The BLF188XR is the current top of the pile for.

The amp you require will have to be linear, so Class AB, so push pull.

Single ended if fine for 'Generators' as you can use class C, E or D but they're NOT linear so cant be used as an amplifier.

Sure you can use class A for an amp, great with it's theoretical 30% eff, typically 20%

Or you can use class D/E generators with theoretical 100%, typical 85-95%.

NO contest in my book...

Str.
'It's better to give than receive' so why Rx when you can Tx!

                                              ;)

Offline digitalmod

  • Hero Member
  • *****
  • Posts: 572
  • Cherokee Foot Hills, SC
  • Freedom includes Radio Broadcasting
    • View Profile
    • Email
Re: Amplifier Topologies and Classes
« Reply #3 on: February 12, 2018, 1459 UTC »
 How much drive does the BLF 188 xr require? I note complete soldered on PC board units without driver and harmonic filter or power supply.
Thanks , just curious. Much amazing stuff available these days in RF :-X
Radio is dying. We need to give it shelter

Offline JimIO

  • Sr. Member
  • ****
  • Posts: 491
  • QTH I.O. MA
    • View Profile
Re: Amplifier Topologies and Classes
« Reply #4 on: February 12, 2018, 1803 UTC »
Good post Str. Generator is the word I should have used.
Have been looking at 13.56 Mhz half bridge D/E on the web but non I have found so far give details on how to make a simple high side driver circuit.

Offline Stretchyman

  • Hero Member
  • *****
  • Posts: 656
    • View Profile
Re: Amplifier Topologies and Classes
« Reply #5 on: February 12, 2018, 2217 UTC »
Please answer the DETAIL questions...!

You can get 200W out of a GaN pair on 20m easy, I have a lash up I can show you.

Digiplod, it's 3W max to drive the 188XR, BTW.

High side driver? You'll only need that for a floating gate of PWM Modj. IR2110 etc has all that built in.

Anyway not sure why you want high side anything.

Do you know what you want/ are doing etc etc???

Str.

p.s. I'm 'concerned' for both of you actually!!
'It's better to give than receive' so why Rx when you can Tx!

                                              ;)