HPA L3 noiseII

  1. What is formula for BJT thermal noise?
    Vnrb= 4kTrbΔf V2
  2. What is formula for Shot noise in BJT what terminals generate them?
    • inb2 = 2qIbΔf A2 
    • inc2 = 2qIbΔf A
    • made by collector and base
  3. what is the knee frequency approach to the formula for flicker noise in BJT? Is it normally included/
    inf2 = (2qf1IbΔf)/f A2

    Not normally included as it is negligible at higher freq compared to other noise mech
  4. Draw the hybrid-π noise model
    Image Upload 1
  5. What is formula for VT
    VT= kT/q
  6. What is MOSFET formula for thermal noise
    Image Upload 2
  7. What is mosfet OG formula for Flicker noise?
    Image Upload 3
  8. What is mosfet formula for shot noise, is it normally considered in calcs?
    • Image Upload 4
    • no not really
  9. Draw equivalent noise model of mosfet
    Image Upload 5
  10. Derive voltage and current noise equations for MOSFET noise model
    • Image Upload 6
    • forget about current noise because gate leakage current is so low.
  11. What input device do you use when you have really low values of Rs?
    Transformer coupling
  12. What input device should you use at midrange impedances? Which should you use for high frequency applications and which should you use for lower rb?
    • Bipolar transistors
    • npn have higher B0 and f
    • The pnps have lower rb
  13. What input device should you use for high values of source impedance? why?
    Whats the drawback
    Use mosfet for low input noise current

    Drawback is that you get 10->100 times greater 1/f noise
  14. What input device should you use for inductive sources?
    • A device with low vn2 and low in2 .
    • This is because:At low frequencies in^2 dominates
    • At high frequencies vn^2 dominates
  15. What input device should you use for sources with parallel capacitance?
    Vn^2 is critical so use a bipolar transistor with a high quiescent collector current to minimise this term
Card Set
HPA L3 noiseII
noise part 2