Defining BJT Noise Equations

Defining BJT Noise Equations

Equations for modeling BJT thermal, shot, and flicker noise are as follows.

Defining Noise Equations

The mean square short-circuit base resistance noise current equation is:


  
The mean square short-circuit collector resistance noise current equation is:


  
The mean square short-circuit emitter resistance noise current equation is:


  
The noise associated with the base current is composed of two parts: shot noise and flicker noise. Typical values for the flicker noise coefficient, KF, are
1e-17 to 1e-12. They are calculated as:


  
where fknee is noise knee frequency (typically 100 Hz to 10 MHz) and q is electron charge.


  


  


  


  
The noise associated with the collector current is modeled as shot noise only.


  

Noise Summary Printout Definitions

RB, V2/Hz	output thermal noise due to base resistor
RC, V2/Hz	output thermal noise due to collector resistor
RE, V2/Hz	output thermal noise due to emitter resistor
IB, V2/Hz	output shot noise due to base current
FN, V2/Hz	output flicker noise due to base current
IC, V2/Hz	output shot noise due to collector current
TOT, V2/Hz	total output noise: TOT= RB + RC + RE + IB + IC + FN

Star-Hspice Manual - Release 2001.2 - June 2001