[EMAIL PROTECTED] wrote:
Nick Palmer wrote:
> Paul wrote:-
> <<You should read about different types of noise -->
>
> http://www.aikenamps.com/ResistorNoise.htm >>
>
> Well, I read this webpage. Maybe you misunderstand. When they say
>
> <<The thermal noise of a resistor is equal to:
> Vt = SQRT(4kTBR)
I see no term for the current in this expression.
>
> where:
>
> Vt = the rms noise voltage
> k = Boltzmann's constant
> T = temperature(Kelvin)
> B = noise bandwidth
> R = resistance >>
>
> you are taking this to mean that the noise voltage is generated solely
> by the temperature of the resistor whether or not there is a current
> flow and this is what the equation seems to suggest; however, this is a
> sound engineer's equation, not a physicist's. I think it means that if
> the resistor is ACTUALLY resisting current, then the noise voltage is
> dependent upon temperature and the "shot noise"
"shot noise" isn't what Paul is talking about.
> depends upon the
> current. I put it to you that when there is no current though the
> resistor, there is no electrical noise at all. Still no free lunch.
I will bet you ***any*** amount of money you are wrong, that thermal
noise does indeed generate a voltage noise without applying any external
voltage to generate current. Hopefully that will put an end to this
silly conversation. :-) Any *real* EE or physicists knows for fact
thermal noise generates voltage noise due to thermal vibrations.
If you want to see thermal noise then get a low noise amp and connect it
to a large resistor.
There is free lunch for *intelligent* thinking beings. :-)
Apples to oranges in this conversation.
IIRC "shot noise" is indeed noise which occurs only when current is
flowing, and has to do with the lumpy nature of the current coming
through the resistor. OTOH there is also thermal noise which is
independent of the current flowing through the resistor. In practical
terms, they _sound_ very different: shot noise is more like popcorn
(ticks and pops), thermal noise is more like angry snakes (a continuous
hiss).
At least that's what I seem to recall from what I learned back when I
thought I wanted to be an EE....
Regards,
Paul Lowrance
