Question 7.18: A student writes the drain flicker noise current of a MOS de...
A student writes the drain flicker noise current of a MOS device as \left[K /\left(W L C_{o x} f\right)\right] g_m^2=\left[K /\left(W L C_{o x} f\right)\right] \left(\sqrt{2 \mu_n C_{o x}(W / L) I_D}\right)^2=2 K \mu_n I_D /\left(L^2 f\right) , concluding that the flicker noise current is independent of W. Explain the flaw in this argument.
A fair comparison must keep both the overdrive and I_D constant as W changes. (If we allow V_{GS} − V_{T H} to change, then the drain voltage headroom also changes.). Thus, we can express the drain flicker noise current as \left[K /\left(W L C_{o x} f\right)\right]\left(4 I_D^2\right) /\left(V_{G S}-V_{T H}\right)^2 , which reveals that the noise current decreases as W L increases.
Related Answered Questions
Question: 7.22
Verified Answer:
Since the thermal and 1 / f noise of M_1 a...
Question: 7.21
Verified Answer:
Viewing A and B as the outputs and modeling the ci...
Question: 7.20
Verified Answer:
To compute the input-referred noise voltage, we sh...
Question: 7.19
Verified Answer:
Illustrated in Fig. 7.45(a), the circuit produces ...
Question: 7.17
Verified Answer:
We model the 1/ f and thermal noise of the transis...
Question: 7.16
Verified Answer:
With the input signal set to zero, this circuit pr...
Question: 7.15
Verified Answer:
Representing the thermal noise of M_1 and ...
Question: 7.14
Verified Answer:
We construct a Thevenin model for the circuits in ...
Question: 7.13
Verified Answer:
To compute the input-referred noise voltage, we mu...
Question: 7.12
Verified Answer:
From (7.47), the input-referred noise voltage is s...