[Milsurplus] Germanium to silicon

[Bob Camp]

Hi

An oscillator certainly works without the diode. I did it that way  
when I converted my LM. The main thing that the diode helps is phase  
noise, if you use the right diode. How much so depends on the FET you  
are using. It also helps stabilize the operating point a little. That  
will improve stability a bit. The diode will drop the output level,  
so it's not a good idea in all cases. You can certainly find examples  
of both in product we ship every day of the week.

Bob


On Aug 31, 2007, at 3:14 PM, Hue Miller wrote:

>
> I agree that the FETs have much higher Gm than the tubes of that era.
> So it may be necessary to dial in realistic to original tube  
> operation overall
> gain by "turning down" the FET from optimum operation.
> As for the bias diode, i have asked a lot of people about that, and  
> looked
> at a lot of circuits - strictly speaking, it is NOT essential, no  
> matter what
> anyone says. A JFET has its own diode equivalent and will generate  
> self-
> bias.  A MOSFET, no - BUT, i have seen one commerically produced VFO
> from the mid-1970s - and i have this device and it works- that does  
> not
> use a bias diode either. ( I wouldn't have predicted that. ) -Hue  
> Miller
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