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Unformatted text preview: 2013 Lecture 13 – Slide 12 Prof. Ming C. Wu 6 Transit Frequency, fT §༊ 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
= g m Z in = g m ⎜ྎ
⎜ྎ jω C ⎟ྏ = 1
⎟ྏ
I in
⎝ྎ T in ⎠ྏ
g
⇒ ωT = m
Cin 2πfT =
EE105, Fall 2013 Lecture 13 – Slide 13 gm
Cπ
Prof. Ming C. Wu Dealing with a FloaDng Capacitance §༊ Recall that a pole is computed by ﬁnding the resistance and capacitance between a node and GROUND. §༊...
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 Fall '07
 KingLiu
 Frequency, Volt

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