Augmented cathode follower.

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pre65
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#1 Augmented cathode follower.

Post by pre65 »

Having read (but not yet understood) the article about augmented cathode followers, I need to ask a question or two.

Here is the article.

http://www.jrossmacdonald.com/jrmpubs/0 ... llower.pdf

On the examples shown the power supply is a twin rail affair, with pos and neg voltages, but not of equal value. So, in practical terms are we talking about a single supply (with plus and minus equal voltage somehow adapted) or two separate supplies, one for pos V and the other for neg V ?
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Mike H
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#2

Post by Mike H »

That's the trouble with these things, such details are not explained fully.

Personally I think it's plus & minus rails, that way in and out are at zero DC, or near enough.
 
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IslandPink
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#3

Post by IslandPink »

I hadn't appreciated that, but it looks like all the examples are configured for input and output at the same level, as Mike says . It looks like it would probably upset the symmetry of the thing to configure it for a large +only supply, and there would also then be a cap somethere in the middle too - the advantage as it is designed there is no cap in the direct signal path .

The supplies will only need to be up to 30-40 mA on each side, if that helps - if you can find a suitable transformer and/or voltage doublers etc .

Nick is the expert on this of course :D as I know he built an ACF2 for the Eimac 100TH driver and maybe also a 211 amp .
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Dave the bass
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#4

Post by Dave the bass »

I think he used it on the OwstonBarker/Gorham 833a too, IIRC the CF O/P could be wound up and and down on a DC level which in turn drove the DC bias of the grid more and more +ve.

Or summat.

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Paul Barker
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#5

Post by Paul Barker »

Dave the bass wrote:I think he used it on the OwstonBarker/Gorham 833a too, IIRC the CF O/P could be wound up and and down on a DC level which in turn drove the DC bias of the grid more and more +ve.

Or summat.

Like.

DTB
correct.
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#6

Post by Mike H »

To get the different rail Voltages for those pdf ccts I expect you could start with equal + & - rails (i.e. a bridge-rectified full-wave TX), then use dropper resistors, decoupled to ground afterward with caps. :?:

I noticed figs 2 - 4 are very like op-amps in basic shape.

Fig 9 is clever, notice 'Ro' can be used to set the o/p to zero relative to ground?
 
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#7

Post by Nick »

Yep two supply rails. The paper is describing the cathode followers, not trying to be a set of easy to follow instruction.

But with respect I would suggest (as I think Dave is trying to do) understanding the problem before trying to understand the solution.
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