Doherty Amplifier

Bob Bruhns bbruhns at
Mon Aug 6 21:31:51 CDT 2007

An interesting alternative is the Taylor linear amplifier.

It's like the Doherty, but without the 90 degree phase shift.  You have one amplifier device with one power supply, and another
amplifier device with a higher voltage supply, both driven from the same basic source, and both feeding the output tank, all

In AM operation, the lower voltage device is running just at saturation at carrier level, and the peak device is just beginning to
conduct.  The RF drive and power voltages and impedance taps on the output tank are such that the peak tube will push the output up
to twice carrier level (4x the power) before saturation if RF drive is increased.  Drive is adjusted as needed.  Carrier efficiency
is about 60%, and peak efficiency is 60% too.  Efficiency falls below carrier level, and it dips between carrier and peak levels,
but all in all it's pretty good.,+1942+Taylor

  Bob, WA3WDR

----- Original Message ----- 
From: "Andre Kesteloot" <andre.kesteloot at>
To: "Mike O'Dell" <mo at>
Cc: "Tacos" <tacos at>
Sent: Monday, August 06, 2007 9:48 PM
Subject: Re: Doherty Amplifier

Indeed, RCA marketed this set up as the Ampliphase.
In my misspent youth, I worked for RCA International, and remember the
Ampliphase transmitters quite well.
It worked very well on the medium wave band (known in the US as the AM
band) but was more difficult to use on HF, mainly because returning it
was quite touchy.
(In HF broadcasting some of the station's transmitters need to be
returned to another HF band every couple of hours of so).


Mike O'Dell wrote:
> Frank Gentges wrote:
>> There were some very fine Doherty transmitters for AM broadcast that
>> generated 50 kW 24/7.  This is a touchy design to get tuned up but once
>> done, it is very good at amplifying high peak to average ratio signals
>> and did not require the high power audio modulator.

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