B. Murmann EE214B Winter 2013-14 – Chapter 5 9
Lookup Function (For Convenience)
>> lookup(nch, 'ID', 'VGS', 0.5, 'VDS', 0.5)
ans =
8.4181e-006
>> help lookup
The function "lookup" extracts a desired subset from the 4-dimensional
simulation data. The function interpolates when the requested points lie off
the simulation grid.
There are three basic usage modes:
(1) Simple lookup of parameters at given (L, VGS, VDS, VS)
(2) Lookup of arbitrary ratios of parameters, e.g. GM_ID, GM_CGG at given
(L, VGS, VDS, VS)
(3) Cross-lookup of one ratio against another, e.g. GM_CGG for some GM_ID
In usage scenarios (1) and (2) the input parameters (L, VGS, VDS, VS) can be
listed in any order and default to the following values when not specified:
L = min(data.L); (minimum length used in simulation)
VGS = data.VGS; (VGS vector used during simulation)
VDS = max(data.VDS)/2; (VDD/2)
VS = 0;
B. Murmann EE214B Winter 2013-14 – Chapter 5 10
Key Question
! How can we use all this data for systematic design?
! Many options exist
– And you can invent your own, if you like
! Method taught in EE214B
– Look at the transistor in terms of width-independent figures of merit
that are intimately linked to design specification (rather than some
physical modeling parameters that do not directly relate to circuit
specs)
– Think about the design tradeoffs in terms of the MOSFET’s inversion
level, using g
m
/I
D
as a proxy