jason9

modified 8 years ago

Efficient AM with Class-E RF Amplifier and Class-D Audio Amplifier

420

06:01:13

Originally by @thebugger. His version used a class-C RF amplifier, and I modified it to be class-E for maximal efficiency.

With a class-E instead of a class-C. I found that the 1mH inductor is plenty of filtering, and that a proper filter is actually quite unstable without a resistive load to soak up the oscillations. The class-E shown here is actually one of the circuits I’ve posted with slight modifications (slight rounding of the values). The 2.67nF capacitor is 2.2nF+470pF.

Edit: New MOSFET setup taking advantage of the fact that it will only ever have to provide current and never receive it. This new setup is complete with a driver stage that includes Schottky diodes to keep the fast changing voltage from going through the parasitic capacitance of the BJTs and charge the off one’s base causing both to turn on resulting in an unnecessary high through current.

Edit 2: I copied this over to a new schematic so that it could be made public instead of unlisted.

published 8 years ago

zorgrian

8 years ago

@jason9 Did you or did you not write "I think that the class-E might just be a very highly optimized version of the class-C. What do you think?"

zorgrian

8 years ago

Yes, for the record Mr smarty-pants, it appears that you DID write thee above with indication and free admission that of class E you did not know jack shit! Indeed, if i didnt know better i would suspect you of being mentored by someone who does your thinking for you....

jason9

8 years ago

Yes, I did write that, but I wasn’t to sure so I asked what you thought of that. But I suppose that there is enough difference between them to be classified as different classes, especially since one has a theoretical 100% efficiency and it very unlikely if even possible that a standard class-C could get above 95% or even 90%. I was just noting that there seemed to be some similarity and wanted to know what you thought of that. I replaced the class-C in @thebugger’s circuit with a class-E as shown here to increase the efficiency.

zorgrian

8 years ago

Were you to actually know anything, it might be deserving to express the need for understanding of the output capacitance belonging to the MOSFET? Eh?

zorgrian

8 years ago

@jason9 have you actually built any circuitry outside of the simulated realm of EC or other simulators?

jason9

8 years ago

Oh, sorry, when I posted my first comment, I hadn’t yet received your second comment. I am not being mentored by someone who does my thinking for me, and as far as I know, I know more electronics than anyone around me thanks to this helpful little app. Unfortunately, the average 13 year old doesn’t have the resources for testing out any electronics in real life, and that includes me since I’m also 13. I have read how MOSFETs are rather capacitive since the structure of an IGBT is essentially the same as that of a capacitor, just with some silicon. That will need to be taken into account in real life, but here in the simulator I just simulate whatever design of circuit works best with the 5pF capacitance of the MOSFETs in the simulator. Also, is it just me, or are you going through some kind of being mean streak? Just yesterday you were being mean against @thebugger about his knowledge and trying to bring completely irrelevant-to-electronics topics into the discussion just to be mean to @thebugger. Also, I have done some reading on class-Es and I do know something about them, like what wave shape at the source (drain? Whichever is the BJT collector equivalent) of the MOSFET is optimal.

zorgrian

8 years ago

You are clearly not an average 13 year old!

zorgrian

8 years ago

However, it would be better to say 'being mean to' , than 'being mean against'. In both cases, the use of mean, in this context is an Americanism

zorgrian

8 years ago

This results in a demoralized state of language

zorgrian

8 years ago

Actually, I was using a soldering iron at the age of 10. I feel, things have become over protective.

jason9

8 years ago

Even if I’m not exactly the average 13 year old (I even scored at 130 on an IQ test which is supposed to be top 3%), that doesn’t mean that I magically have all the resources I could possibly need and as much money as I want to throw away on electronics, or even be able to use a soldering iron without parent supervision if at all.

jason9

8 years ago

The only electronics that I have at home is an electronic playground with a bunch of resistors, capacitors, an inductor, three diodes (silicon and germanium), an audio transformer, a speaker, three LEDs (I think I might have burned one out), a seven segment display, a couple of OP-amps, 4 NAND gates, and three transistors (an NPN and two PNP), which your supposed to be able to do a lot of things with, but the best I could come up with is an uneven PNP astable multivibrator (since I didn’t have all the values one side had higher capacitance and lower resistance while the other side had lower capacitance but higher resistance). So, there’s not really a lot I can do, especially considering that I only have three transistors.

hurz

8 years ago

@jason9, But this minimalistic number of components make and keeps you creative! @zorgrian, what i saw from janson and class e, he quite good understand how it why it works better then class c. I have also sometimes the feeling jason is more around 20+ anyway, why shall a 20+ guy tell us he is just 14? Does this make sense?

zorgrian

8 years ago

Yes i am also unsure of this 13 business. Either we are dealing with a very exceptional young man or we are dealing with another type of exception!

zorgrian

8 years ago

I agree that there is more hidden here than is revealed. Yet, it is just possible that we are dealing with a young genius? On the other hand, i would remind our young friend, that showing off about one's IQ is rather ugly and in my experience does you little favours.

radpb

8 years ago

Yeah, but we can forgive him for the faux pas of posting his IQ. We all do irritating things when we're young. He'll just know now that posting your IQ is just as irritating as saying "I am very smart."

hurz

8 years ago

@radpb, thats why young people with high IQ do get in trouble if they tell in public how high its IQ is. And they are outsider.

jason9

8 years ago

I am indeed 13, but I do very much enjoy doing things like reading about chemistry and physics and such on wikipedia, and I also enjoy doing other things like messing around with circuits on EC and cellular automata on golly, but I’m not so into games that most kids my age play, but I do still like a few games such as Terraria and Minecraft (with mods, the normal version is just plain boring).

jason9

8 years ago

Is there anything I could possibly do to prove that I’m 13? I don’t exactly mind being thought of as 20+, but it would probably be better if everyone new my actual age.

hurz

8 years ago

No chance. Keep to be a little more scilence. You have no other chance.

crake

8 years ago

@Jason9 Keep up the great work and stay curious and rigorously devoted to everything you find interesting. Your age doesn't matter here, and shouldn't matter here. We are here for circuit design, and you do that incredibly well.

jason9

8 years ago

Ok.

zorgrian

8 years ago

Except for the provoking, the profanities, the general stance of disproof of validity of another's work by accusations of being gay, a genetically impoverished inbreeding chimpanzee! All of which is completely normal for the 13 year old... --- ...

zorgrian

8 years ago

Wait, hold on, I mean saying such profanity is normal for MOST 13 year old persons. Thus, evidence of being as ridiculous as the rest of us here is required!

zorgrian

8 years ago

If indeed, 13 this individual is, as the gender and tendencies of said person are not relevant, then it follows that the list of activities is sadly lacking in social face to face meeting. Again, this is concomitant with very early teenage life in the current network driven era. It may be a defining character of the zeitgeist!

zorgrian

8 years ago

In other words grasshopper, get thee out and about! Unless ye haveth some physical impedance, first thee must walk across rice paper. Make no sound!

angel17666666766

8 years ago

Wow very cool

zorgrian

8 years ago

What is 'wow very cool' ?

hurz

8 years ago

@crake @jason9, dont get me wrong with "scilence" I mean do not go and tell others you have made a test and the result was 130+ First those tests are quite questionable and do test things which might be importante for completely different topics in knowledge. Second, just keep it for you, people will notice it anyway even you do not tell them, sooner or later ;-) keep up your good circuits here on everycircuit!

crake

8 years ago

@Hurz I completely agree with that.

zorgrian

8 years ago

I also agree. But will add that IQ as standardized, is an oxymoron. Statistically, the subjects that are tested do so for exceptional reasons, such that the baseline of the normal distribution curve is necessarily altered. That is to say that there are far more results from the extremes of these test results than those which would fall within the middle section. Thus, over time the test itself becomes more and more inaccurate....

jason9

8 years ago

Yeah, IQ tests are quite inaccurate.

zorgrian

8 years ago

@jason9, with respect, yee must demonstrate some form of eccentric oddity! Though canst not be a complete nerd here! Otherwise it shall be possible to replace thyne personage with an automomiton or facsimile! Hasten!

zorgrian

8 years ago

Another possible scenario, is that thee said Jason9 unit is a bot inserted by the CIA, KGB, MI7, NWO, BBC, FOX, ABC, et. al.

jason9

8 years ago

It’s a bit hard to understand you between the misspellings and words like “facsimile”. Now that I’ve looked it up I know that it means exact copy, but I didn’t know that before. Also, I am NOT a robot. Do you mean automaton by “automomiton”?

maxmax_66

8 years ago

@jason9. Don't let it get to you. You seem intelligent, articulate and determined with an impressive conceptual grasp of the field. Additionally, your curiosity, resourcefulness and stubbornness will most certainly prevent the wilting of your potential. In the context of previous threads, I only hope you fully embrace the power of mathematics to efficiently communicate your concepts to your potential future peers. Keep up the good work.

maxmax_66

8 years ago

That being said, you're 13. Don't forget to have fun.

zorgrian

8 years ago

Hmm possible precocious nature? I am dyslexic so yes i may make spelling mistakes. However, i can assure you that my intelligence is not diminished by certain inabilities.

zorgrian

8 years ago

You dont write like any 13 year old that i have ever encountered

zorgrian

8 years ago

Also yes, your nature reads like a square, a nerd, and begs the question, what is your real age?

hurz

8 years ago

@jason9 ist ein 35 Jahre alter Bulle, der in einer Polizeizentrale irgendwo sein Netz im Netz ausgelegt hat, um auf Kinderschänder zu warten? Ist es das was du denkst @zorgrian?

jason9

8 years ago

@hurz, could you translate that please? @zorgrian, I simply really don’t like spelling mistakes. I reread everything I write at least once to check for errors. I try to keep grammar mistakes to a minimum, but I’m not as good with knowing where commas go, although I get it right most of the time.

hurz

8 years ago

@jason9, now you see what my and anybody else situation is if we are not speaking english as mother tongue? So be for a while in the same situation and do your best, I dont help you! Good luck!

zorgrian

8 years ago

@jason9nerdHead, I simply do not believe you at all. You are most probably a policeman with a covert agenda working for a foreign power

zorgrian

8 years ago

What do you say @hurz? Imposter or 13 year old? And which motive does this square head have ?

zorgrian

8 years ago

@liar9, I do not like people who concentrate upon stupidity, narrow minded square headed aspects of life such as spelling! No! I detest this aberration in character and fluidity of mindset.

zorgrian

8 years ago

Whatever your true age is, your vibe is repugnant!

maxmax_66

8 years ago

@zorgrian. Easy, no need to harsh the communal mellow. Leave the conspiracy theories to the Orange Demon.

zorgrian

8 years ago

Which conspiracy? Conspiring to do something is fairly commonplace.

zorgrian

8 years ago

I will, however, taper down thee said vibration, so thusly does it mellow out into the vastness.

hurz

8 years ago

Lets suppose he is 13, we just take an eye on @jason9, so he wont get lost in this nasty commmunity.

zorgrian

8 years ago

Just in case he is 13, I shall treat him/ her according to the age stated. Thus, if precocious statements are issued by the young person, i shall either totally ignore this or and discipline said behavior.

zorgrian

8 years ago

I do not accept the ridicule intended by this person in respect of my dyslexia. It is not acceptable from a 13 year old nor from any other person.

hurz

8 years ago

Ok, does this help you zorg? He don't know what he's saying, he's just a not well educated 13 year old little kid. We all know and can agree on that, right?

maxmax_66

8 years ago

I agree with hurz. I see no intentional malice nor overt hostility on the part of jason9. Maybe your typical socially underdeveloped 13 year old, but I see little reason to doubt his sincerity. It would be a shame to scare or shame him into silence on simple conjecture.

hurz

8 years ago

He does get older and older and older, and one day, if we are still there, we might laugh about him.

zorgrian

8 years ago

OK, I suppose my life taught me lessons as is true for each of us. I learned not to judge by what a person cannot do but by how they seem to treat others; I had to learn this fast as my disability with spelling, sequences and other stuff, resulted in judgement of myself. I knew perfectly well at 13 that I was very intelligent, yet unable to spell of recite times tables. Sadly, my better disposition toward differences, my lack of judgment of those who seemed to judge me harshly, did not survive so well into my adult years. This, is a reminder of such judgment. I agree that no malicious intent has been demonstrated, yet the smug self righteous display is not clever and could become ugly very quickly. There is also an apparent lack of humor, unless this is actually a disability?

zorgrian

8 years ago

I also agree with the idea of forgiveness. "Forgive them for they know not what they say". The grand question is, do we forgive every action? Those who appear to seek to deceive whole populations, nations and even themselves, so that they achieve some doubtful interpretation of greater good? I suggest even if those who do such things, in a deep sense, do not know what they are doing, we may forgive their ignorance, but not their action.

hurz

8 years ago

Das wird aber sehr philosophisch, die Frage inwiefern ist ein Individuum verantwortlich für das was er macht und tut. Ich wurde nicht gefragt, ob ich auf dieser Welt Verantwortung übernehmen möchte! Wir sind hier alle hinein gestossen worden. Aber das erlaubt uns natürlich auch nicht ein Schwein zu sein, diese Lizenz haben wir auch nicht mitbekommen.

zorgrian

8 years ago

Ja, wir alle kommen hier an und dann werden wir durch eine ganze Reihe von Einflüssen zu dem was wir sind. Nichts davon rechtfertigt die Haltung des Schweinehundes

zorgrian

8 years ago

Also, in connection with this circuit 1) 1 mH is quite large, 2) The function of this coil is not primarily a filter. It stores energy which is dumped through the FET.

hurz

8 years ago

Zorg, this is an AM modulator which is modulated via the power supply. Audio is made by a digital amp and the choke is transparent for this frequency in impedance below 100 Ohm. While it blocks RF frequencies, its impedance it above 3kOhm. So modulating the supply makes it a nice AM modulator. The class E RF amp is in resonance with the output filter, this is the difference to a simpler class C where the outfilter is independend to the amp itself. But here its part of the amp and must be tuned in timing to stay at perfect efficency for the switching transistor.

zorgrian

8 years ago

Hurz, thanks for the total clarification. As always, you are correct. I just looked at thee circuit with your explanation in mind and now see it differently. Indeed, I have played around with the said 'tuning'. I would like to build one of these it is interesting!

hurz

8 years ago

I would like to do something with this device in class E mode PTFA210701E I have one LDMOS from infineon

zorgrian

8 years ago

But of course, with the class D audio running at say 30 - 50 kHz and definitely not up at the same frequency used as the carrier wave.

zorgrian

8 years ago

As mentioned before, this RF 'chopping' of audio is unnecessary and liable to produce additional problems. Its just easier to see it all working in the simulation with the both ends of this class D class E system running at the same frequency.

hurz

8 years ago

What you call chopping is what makes a class d so efficent. And right, it does cause terrible problems in harmonics! But the headline is for efficient AM, and not for noise free AM 😁

zorgrian

8 years ago

I specifically said RF chopping meaning Radio Frequency. Thus, if we reduce the chopping to 30 kHz which is above human hearing, and then use a more standard output filter before the choke, then this might be better?

zorgrian

8 years ago

But for a demo on the subject of class D and E AM transmission, not bad I think!

zorgrian

8 years ago

Happy Easter to all

hurz

8 years ago

Yeah, but going down in sampling frequency cause bad results for the audio, cause its importante for the DAC which a class D is to have a high oversampling 1Bit DAC. So the way might be go up in frequency and watch the harmonics 3. 5. 7. To not hit the transmitter frequency. The filter is quite limited in change, cause its impedance must match or we get ringing or bad performance in filter characteristics. Happy weekend, and relax a few days!

zorgrian

8 years ago

Update: I've been experimenting with this setup at low power. I was wrong insofar as the modulated class D chopping frequency must be at the same frequency and phase for this system to work as class E. If these frequencies are different or worse out of phase, then it results in non class E output. Effectively, the FET is often part turned on which produces heat. However, a lower frequency of audio chopping frequency does produce part class E when it is in phase with the output carrier of RF signal. In practice, a PLL system might work, and this might be needed even when both chopping audio and carrier frequencies are the same.

jason9

8 years ago

I don’t see the issue in this circuit if I change phase or frequency. Maybe you reduced the 1mH inductor?

zorgrian

8 years ago

Briefly, the issue is with harmonics - I really like this idea and your latest one is much better. I have been building similar circuits in the workshop. In practice, I have been using the BS170 at lower voltages than in your mega transmitter.

zorgrian

8 years ago

I have measured the output of three BS170 transistors in parallel - produces just under 5 watts @ 12 volts with a different (simpler, not as good but quick to build) low pass filter.

zorgrian

8 years ago

http://everycircuit.com/circuit/6185559516250112

hurz

8 years ago

Zorg, the frequency dependencies you see from class D to class E is only the case here in simulation. Everycircuit needs the frequencies close enough to get proper results, if they are to different everycircuit fails in simulation. But in real they are completely independent!

hurz

8 years ago

Zork, I guess you look for a 7MHz RF project, right? Sure at 7MHz problems will start at gate driver for the mosfet, even sooner below 1MHz. For 500kHz it might be easy.

add comment in editor