Unformatted text preview: source overlap/fringing capacitance à༎ CGS – C2 in parallel with the drain overlap/fringing capacitance à༎ CGD EE105, Fall 2013 Lecture 21 – Slide 10 Prof. Ming C. Wu 5 Example …with MOSFET capacitances
explicitly shown CS stage Simplified circuit for
highfrequency analysis Lecture 21 – Slide 11 EE105, Fall 2013 Prof. Ming C. Wu Transit Frequency §༊ The “transit” or “cut oﬀ” frequency, fT, is a measure of the intrinsic speed of a transistor, and is deﬁned as the frequency where the current gain falls to 1. Conceptual setup to measure fT I out = g mVin
I in = Vin
Z in !1$
I out
= gm Zin = gm #
& =1
I in
" jωT Cin %
⇒ ωT = gm
Cin 2π fT = EE105, Fall 2013 Lecture 21 – Slide 12 gm
CGS
Prof. Ming C. Wu 6 Small Signal Model for CS Stage λ =0 EE105, Fall 2013 Lecture 21 – Slide 13 Prof. Ming C. Wu … Applying Miller’s Theorem ω p ,in =
ω p ,out = 1
RThev (Cin + (1 + g m RD )CGD )
1
⎛ྎ
⎞ྏ
⎛ྎ
1 ⎞ྏ
⎟ྏ
RD ⎜ྎ Cout + ⎜ྎ1 +
⎜ྎ g R ⎟ྏCGD ⎟ྏ
⎟ྏ
⎜ྎ
m D ⎠ྏ
⎝ྎ
⎝ྎ
⎠ྏ Note that ωp,out > ωp,in
EE105, Fall 2013 Lecture 21 – Slide 14 Prof. Ming C. Wu 7 Direc...
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This note was uploaded on 01/22/2014 for the course EE 105 taught by Professor Kingliu during the Fall '07 term at Berkeley.
 Fall '07
 KingLiu
 Frequency

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