Shot Noise By Colector

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Rambotronics

Joined Feb 6, 2023
10
Hello,

I have a pnp common emitter stage, shown in the attached picture. Does anyone know why my collector shot noise gets attenuated as i increase the emitter resistor R1? For R1=0 the collector shot noise totally dominates the circuit noise at LOAD and as I increase the emitter resistor to 1kohms, it gradually lowers until the noise produced is neglictable. Keep in mind that even doe i'm changing the emitter resistor, the current through the Load R2 (ic) is always 1mA. ishot^2 /df = 2 q ic ;The circuit in the picture is incomplete but it is the important part, the base is properly biased and the transistor is always at the active zone .

Hopefully someone can help me!! Thank you.
 

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joeyd999

Joined Jun 6, 2011
5,417
Been a while: IIRC, the shot noise visible on the collector should be β times the shot noise generated by the base current through the b-e junction.

Since the base current is *much* smaller than the collector current -- in addition to amplified -- any shot noise developed at the collector should be negligible by comparison.

Now, how this figures into your observations is something I don't have time to think about.
 

DickCappels

Joined Aug 21, 2008
10,246
The schematic seems incomplete. For one thing, what is the base connected to? What is the manufacturer and part number of the transistor? What voltages are involved?

is your circuit a physical circuit or is it simulated?
 
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