Return-Path: X-Spam-DCC: paranoid 1233; Body=3 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_MESSAGE,HTML_TINY_FONT autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u1MJIo0X006453 for ; Mon, 22 Feb 2016 20:18:50 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aXvwx-0006HD-LL for rs_out_1@blacksheep.org; Mon, 22 Feb 2016 19:15:15 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aXvwx-0006H2-5W for rsgb_lf_group@blacksheep.org; Mon, 22 Feb 2016 19:15:15 +0000 Received: from mail-wm0-f43.google.com ([74.125.82.43]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1aXvvt-0007dA-4i for rsgb_lf_group@blacksheep.org; Mon, 22 Feb 2016 19:15:14 +0000 Received: by mail-wm0-f43.google.com with SMTP id c200so187324802wme.0 for ; Mon, 22 Feb 2016 11:13:53 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=PJb1fJAOPbRek+5Tmz2IQabgjn8SbtbzRc+BCMuMjF8=; b=Suu3LwZzaWNpaoN9JM2bUgM/VXdKJuoZCjCwvTdZ1wqzhBsQx13gkePLhJzFgioWgW 9nAIXTkMajuTRkq0ijIVnWNTxhSMNXP35E0rgnDkyMQtVvdbTY8b7cUcQv6MFDWDBZTR 6ZDZ2ugeg4Cd6/tuSpE6ilG+te7CT+kN9ihNEUHv2H+I9U+qnY9sGvNPf1wIsmIw+2f2 LKaiZSB+xU1xmBxLoWHI7hjDEuIiUtG1QqHmoXRXu4KiPf42yP9iOh3gWMhwZLR8etil Jl5Z97ezQBlWhvovWPRkV90oGpHCImilmzPqrpCuJqdTAgdG5Me2mPlbQhbGIgG/J7cN 58jw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=PJb1fJAOPbRek+5Tmz2IQabgjn8SbtbzRc+BCMuMjF8=; b=BOQC5Iu1MGRV4WKGAj6+VEV3YOPf9E568N4y08Wjgme6nKl1VthRfW730XDn0lQ+gg IvUHXdzxQUSyIDRz7ehHj30e1PerJdqdpoH8iCGERfzdopGtN0Wr4S5uXkdYquwougzq hbKFSWtRpfJjtb0omPEjTM0EuPjJ6WhkjIf0PWKh67hrK0p3lSWBeCdCX79Y3gA4oK23 iuJFNp6/RS4Liy2nfBSwwiwRXn+odeYSo5WI9QL0LMrYWLZNMcBRtNcPHfYmOJ2cD63Z xO+FAuekBxQqphtLGW7pS4YS4X2+mSKz2MA2xVKjUvYadsr+MHj7ulR5aFwWpU0JK5bw sM9g== X-Gm-Message-State: AG10YOSeWN3XAZfUPtEzHLndBye0fVUoB6te4PAvJA6lkdz4Z8T+P5U4WubMecuwtOZeYlQxN8D9flWcW5+CjA== MIME-Version: 1.0 X-Received: by 10.194.113.130 with SMTP id iy2mr14743061wjb.56.1456168387899; Mon, 22 Feb 2016 11:13:07 -0800 (PST) Received: by 10.28.187.213 with HTTP; Mon, 22 Feb 2016 11:13:07 -0800 (PST) In-Reply-To: <7E7DFBB4D102A04DB5ADC88D66628A4A444D7A6C@ICTS-S-MBX1.luna.kuleuven.be> References: <7E7DFBB4D102A04DB5ADC88D66628A4A444D7A4A@ICTS-S-MBX1.luna.kuleuven.be> <7E7DFBB4D102A04DB5ADC88D66628A4A444D7A6C@ICTS-S-MBX1.luna.kuleuven.be> Date: Mon, 22 Feb 2016 19:13:07 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org Cc: "rsgb_lf_group@yahoogroups.co.uk" X-Scan-Signature: 3d57f46aaa11dced1062afcdaf02fb40 Subject: Re: LF: RE: [rsgb_lf_group] Single Stage Class-B Content-Type: multipart/alternative; boundary=001a1130cffc7e7e69052c609fa5 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: RO X-Status: X-Keywords: X-UID: 6945 --001a1130cffc7e7e69052c609fa5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable That is the task of the resonant tank circuit, to maintain the RF current flow throughout the device during the off period. During the off period, the drain volts have to fly up to 2.Vdd to keep it operating linearly, and the resonant network has to ensure that happens. The concept is quite standard, used for most bipolar and FET output stages at low power (watts, tens of watts) at VHF and UHF. Although I've noticed that modern FET amplifier modules do run at a higher standing current and lower efficiency than bipolar ones. All the old valved SSB transmitters of a bygone era use that topology I may need another long walk to ponder in more depth ... Andy G4JNt On 22 February 2016 at 18:53, Rik Strobbe wrote: > A single stage class B amplifies the signal over 180 degrees (ie. half th= e > sine). > > As long as the amplifier is not saturated the amplitude at the output is > almost linear proportional to the input amplitude, but the signal is > distorted due to the fact that half of the sine is missing. > > In a class B push-pull each FET (or bipolar transistor, tube) will amplif= y > the "opposite" 180 degrees of the input signal and these will combine at > the output , so apart from the cross-over distortion the output signal in > pretty undistorted. > > > > 73, Rik ON7YD - OR7T > > > ------------------------------ > *Van:* rsgb_lf_group@yahoogroups.co.uk [rsgb_lf_group@yahoogroups.co.uk] > *Verzonden:* maandag 22 februari 2016 19:39 > *Aan:* rsgb_lf_group@yahoogroups.co.uk > *CC:* rsgb_lf_group@blacksheep.org > *Onderwerp:* Re: [rsgb_lf_group] Single Stage Class-B > > > > There's nothing inherently "more linear" about push pull over a single > stage, given you run the same device at the same power per stage (ie half > the PP level) > > 'jnt > > > On 22 February 2016 at 18:34, Rik Strobbe rik.strobbe@fys.kuleuven.be > [rsgb_lf_group] wrote: > >> >> >> Hello Andy, >> >> >> >> the advantage of a push-pull class B amplifier is that it it pretty >> linear at higher power levels. >> >> >> >> 73, Rik ON7YD - OR7T >> >> >> ------------------------------ >> *Van:* rsgb_lf_group@yahoogroups.co.uk [rsgb_lf_group@yahoogroups.co.uk] >> *Verzonden:* maandag 22 februari 2016 18:31 >> *Aan:* rsgb_lf_group@blacksheep.org; rsgb_lf_group@yahoogroups.co.uk >> *Onderwerp:* [rsgb_lf_group] Single Stage Class-B >> >> >> >> Whilst out walking and pondering, as one does.... >> >> There are hundreds of designs out there for linear power amps using >> FETS. They all use a similar design, push-pull with centre tapped ferri= te >> cored transformers at input and output, often with resistive feedback - = and >> all broadband. The design is so standard it's become tedious ... and a= s I >> don't do tedious, it made me think: >> >> Back in days of yore when those big bottles ruled the roost , apart fro= m >> a few designs for UHF, they were all single ended. >> >> So, why not a single ended MOSFET amp (for single band operation)? >> We're used to seeing single device for class-E, where the tank circuit >> does much of the waveform cleaning, and reduces the low pass filter >> requirements. So what's wrong with a tank-based design for class-B? >> >> A single ended amp can even be made ferrite free (although a final >> stage DC feed choke would no doubt benefit from it). Apart from a few >> very low power designs, I don't recall seeing any designs for single ban= d >> ferrite free linear amps using power MOSFETS. >> Only major downsides I visualise is that load resistance at the device i= s >> 4 times lower for the same Vdd and Pout , and device dissipation is doub= led >> >> Has no one ever bothered, because broadband transformer push-pull is so >> straightforward? >> Has a trick been missed? >> >> Andy G4JNT >> >> >> > __._,_.___ > ------------------------------ > Posted by: Andy Talbot > ------------------------------ > Reply via web post > > =E2=80=A2 Reply to sender > > =E2=80=A2 Reply to group > > =E2=80=A2 Start a new topic > > =E2=80=A2 Messages in this topic > > (3) > Visit Your Group > > > > [image: Yahoo! Groups] > > =E2=80=A2 Privacy =E2=80=A2 > Unsubscribe > =E2= =80=A2 Terms > of Use > > . > > __,_._,___ > --001a1130cffc7e7e69052c609fa5 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
That is the task of the resonant tank circuit, to maintain= the RF current flow throughout the device during the off period.=C2=A0
During the off period, the drain volts have to fly up to 2.= Vdd to keep it operating linearly, and the resonant network has to ensure t= hat happens.

The concept is quite standard, used for= most bipolar and FET output stages at low power (watts, tens of watts) =C2= =A0at VHF and UHF. =C2=A0 Although I've noticed that modern FET amplifi= er modules do run at a higher standing current and lower efficiency than bi= polar ones. =C2=A0 All the old valved SSB transmitters of a bygone era use = that topology

I may need another long walk to pond= er in more depth ...

Andy =C2=A0G4JNt
<= /div>

On 22 Februa= ry 2016 at 18:53, Rik Strobbe <rik.strobbe@fys.kuleuven.be&g= t; wrote:

A single stage class B amplifies the signal over 180 degrees (ie. half t= he sine).

As long as the amplifier is not saturated the amplitude at the output is= almost linear proportional to the input amplitude, but the signal is disto= rted due to the fact that half of the sine is missing.

In a class B push-pull each FET (or bipolar transistor, tube) will ampli= fy the "opposite" 180 degrees of the input signal and these will = combine at the output=C2=A0, so apart from the cross-over distortion the ou= tput signal in pretty undistorted.

=C2=A0

73, Rik=C2=A0 ON7YD - OR7T

=C2=A0

=C2=A0

There's nothing inherently "more linear" about push pull= over a single stage, given you run the same device at the same power per s= tage (ie half the PP level)=C2=A0=C2=A0=C2=A0=C2=A0

'jnt


On 22 February 2016 at 18:34, Rik Strobbe rik.strobbe@fys.kuleuven.be [rsgb_lf_group] <rsgb_lf_gro= up@yahoogroups.co.uk> wrote:
<= /u>
=C2=A0

Hello Andy,

=C2=A0

the advantage of a push-pull class B amplifier is that it it pretty line= ar at higher power levels.

=C2=A0

73, Rik=C2=A0 ON7YD - OR7T

=C2=A0

Van: rsgb_l= f_group@yahoogroups.co.uk [rsgb_lf_group@yahoogroups.co.uk]
Verzonden: maandag 22 februari 2016 18:31
Aan: rsgb_lf_group@blacksheep.org; rsgb_l= f_group@yahoogroups.co.uk
Onderwerp: [rsgb_lf_group] Single Stage Class-B

=C2=A0

Whilst out walking and pondering, as one does....

There are hundreds of designs out there for =C2=A0linear=C2=A0power am= ps=C2=A0using FETS.=C2=A0 They all use a similar design,=C2=A0push-pull wit= h centre tapped ferrite cored transformers at input and output, often with = resistive feedback - and all broadband.=C2=A0=C2=A0 The design is so standard it's become tedious ... and=C2=A0as I don't=C2=A0do tedio= us, it made me think:

Back in days of yore when those big bottles ruled the roost ,=C2=A0 ap= art from a few designs for UHF, they were all single ended.

So, why not a single ended MOSFET amp (for single band operation)?=C2= =A0=C2=A0 We're used to seeing=C2=A0single=C2=A0device=C2=A0=C2=A0for c= lass-E, where the tank circuit does much of the waveform cleaning, and redu= ces the=C2=A0low pass filter requirements.=C2=A0=C2=A0=C2=A0 So what's = wrong with a tank-based =C2=A0design for class-B?

A single ended=C2=A0amp can even be made ferrite free (although=C2=A0a= final stage=C2=A0DC feed choke would no doubt benefit from it).=C2=A0=C2= =A0 Apart from a few very low power designs, I don't recall seeing any = designs for single band ferrite free linear amps using power MOSFETS.=C2=A0
Only major downsides=C2=A0I=C2=A0visualise is that=C2=A0load resistanc= e at the device is 4 times lower for the same Vdd and Pout , and device dis= sipation is doubled

Has no one ever bothered, because broadband transformer push-pull is s= o straightforward?
Has a trick been missed?=C2=A0=C2=A0

Andy=C2=A0 G4JNT



__._,_.___
Posted by: Andy Talbot <andy.g4jnt@gmail.com>
Reply via web post =E2=80=A2 Reply to sender =E2=80=A2 Reply to group =E2=80=A2 Start a new topic =E2=80=A2 Messages in this topic (3)
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