[AMPS] Setting the record straight--Dick Ehrhorn

[2]

>on 7/18/01 12:03 PM, 2 at 2@vc.net wrote:
>
>> 
>> /\  Designing an unconditionally-stable HF/MF amplifier is more difficult
>> than designing a stable amplifier for VHF.   Although I have heard
>> reports thereof, I have never seen parasitic damage in a VHF or UHF
>> amplifier.  
>
>I gotta throw my 2 cents in on this one because this statement is just not
>completely accurate.
>
>Building a stable amplifier that has high gain becomes increasingly
>difficult the higher ones goes in frequency.  

/\  Are we talking about gain or stability?

> Things such as layout issues,
>bypassing and genuine parasitics become critical.  
>parasitics" I don't mean the kind Rich talks about.  I am talking about the
>inherent, real world, stray inductances and capacitances in components.
>
/\  There are components that don't have stray L?   

>Rich's statement could argued to be correct only because generally we hams
>build our HF/MF amplifiers to be pretty broad banded in their coverage.
>Sure we may have different tuned circuits for different bands, but the
>amplifier in general covers a very large percentage bandwidth.  For
>simplicity's sake let's say the HF band is from 1 to 30 MHz, centered at 15
>MHz (I know it starts higher than 1 MHz).  An amp designed to cover this
>basically is designed for nearly 200% bandwidth! (Percentage bandwidth is
>defined as the total bandwidth covered divided by the center frequency *
>100).  Our bandwidth is 30MHz - 1 MHZ = 29 MHz. %BW = (29/15)*100 which is
>approximately 200%.

/\  new math?
>
enough

> ...

-  R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.  
end


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