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From: Hammy on 14 Apr 2010 17:23
On Wed, 14 Apr 2010 14:35:57 -0500, Vladimir Vassilevsky
<nospam(a)nowhere.com> wrote:

>
>
>Hammy wrote:
>
>> Is it possible to reduce crossover distortion on a push-pull buffer in
>> a package where the bases are tied internally?
>
>Bridge feed forward compensation:
>
>http://www.abvolt.com/misc/feedfwdbridge.jpg
>
>If the bridge is balanced (R1 x R2 x C = L), then the compensation is
>perfect.
>
>
>Vladimir Vassilevsky
>DSP and Mixed Signal Design Consultant
>http://www.abvolt.com
>
>
>
Thanks

I'll try that as well.
From: George Herold on 15 Apr 2010 13:37
On Apr 14, 3:35 pm, Vladimir Vassilevsky <nos...(a)nowhere.com> wrote:
> Hammy wrote:
> > Is it possible to reduce crossover distortion on a push-pull buffer in
> > a package where the bases are tied internally?
>
> Bridge feed forward compensation:
>
> http://www.abvolt.com/misc/feedfwdbridge.jpg
>
> If the bridge is balanced (R1 x R2 x C = L), then the compensation is
> perfect.
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com

That's pretty cool Vladimir. Can I think of this has balancing two
times R1*C and L/R2? And if that is correct, do you pick the time to
be faster than than the highest frequency of interest? Or is there a
better way to think about the circuit.

George H.
From: Paul Keinanen on 16 Apr 2010 01:24
On Wed, 14 Apr 2010 14:35:57 -0500, Vladimir Vassilevsky
<nospam(a)nowhere.com> wrote:

>
>
>Hammy wrote:
>
>> Is it possible to reduce crossover distortion on a push-pull buffer in
>> a package where the bases are tied internally?
>
>Bridge feed forward compensation:
>
>http://www.abvolt.com/misc/feedfwdbridge.jpg
>
>If the bridge is balanced (R1 x R2 x C = L), then the compensation is
>perfect.

Looks quite similar to the "current dumping" feed forward system used
in the Quad 405 power amplifier a few decades ago.

When the Quod 405 was introduced, there was a lot of discussion about
this kind of topologies for instance in Wireless World. This might
help googling for similar systems.

From: Jan Panteltje on 16 Apr 2010 07:04
On a sunny day (Fri, 16 Apr 2010 08:24:01 +0300) it happened Paul Keinanen
<keinanen(a)sci.fi> wrote in <omsfs55s7ogqueqt9ccsoqmsuvt4d467ao(a)4ax.com>:

>On Wed, 14 Apr 2010 14:35:57 -0500, Vladimir Vassilevsky
><nospam(a)nowhere.com> wrote:
>
>>
>>
>>Hammy wrote:
>>
>>> Is it possible to reduce crossover distortion on a push-pull buffer in
>>> a package where the bases are tied internally?
>>
>>Bridge feed forward compensation:
>>
>>http://www.abvolt.com/misc/feedfwdbridge.jpg
>>
>>If the bridge is balanced (R1 x R2 x C = L), then the compensation is
>>perfect.
>
>Looks quite similar to the "current dumping" feed forward system used
>in the Quad 405 power amplifier a few decades ago.

Exactly, and I used it in a 150 kHz 'RF' amp around 1982 or so.
From: George Herold on 16 Apr 2010 09:55
On Apr 16, 1:24 am, Paul Keinanen <keina...(a)sci.fi> wrote:
> On Wed, 14 Apr 2010 14:35:57 -0500, Vladimir Vassilevsky
>
> <nos...(a)nowhere.com> wrote:
>
> >Hammy wrote:
>
> >> Is it possible to reduce crossover distortion on a push-pull buffer in
> >> a package where the bases are tied internally?
>
> >Bridge feed forward compensation:
>
> >http://www.abvolt.com/misc/feedfwdbridge.jpg
>
> >If the bridge is balanced (R1 x R2 x C = L), then the compensation is
> >perfect.
>
> Looks quite similar to the "current dumping" feed forward system used
> in the Quad 405 power amplifier a few decades ago.
>
> When the Quod 405 was introduced, there was a lot of discussion about
> this kind of topologies for instance in Wireless World. This might
> help googling for similar systems.

Thanks for the hint. For any interested there is a link to a paper by
PJ Walker down the bottom of this site that does a good job of
describing what's going on.

http://www.quad405.com/

George H.
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