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37 Threads found on edaboard.com: Inversion Channel
I have read BSIM manual for charge partition in channel. However I don't understand one thing; when using 0/100 charge partition scheme while all of inversion charge is accounted by source node, how is capacitance measured (since Cdb = dQd/dVb). Thanks.
That would want some more details on just how far below VTH. In weak inversion, it's still inversion and channel carriers will be source species. In depletion you may still see some state- or trap-hopping / tunneling transport. But I question altogether the validity of saying a FET will be biased by an arbitrary current and an unknown (...)
That's one of the tricky bits about FDSOI. The body can assume a range of potentials and can be charge pumped, although at DC the B-S diode conduction and D-B leakage currents will sum to "something". Usual MOS equations refer to Vgs, not Vgb although the body potential does have a significant role. Fully depleted seems to be taken to mean mo
I think this cannot simply be differentiated, because both effects (and hot-electron effects, additionally) depend on external conditions: Vds, operation region (strong, light or no saturation), and operation mode (strong, moderate or weak inversion) with different dependencies. I'd suggest to study these different ef
Good for decoupling applications where you can count on the DC voltage you need to drive full inversion and low "access resistance" (channel). Poor for applications where you require low variation in C across a wide range of DC bias (or large signal operation). CV swing can give you harmonic distortion issues in RF and analog amplifiers. This is w
A MOSCAP requires a minimum voltage across it to give the maximum capacitance. It gives the maximum capacitance when it is in strong inversion i.e. the Vgs > Vth when the channel is full formed. Check Razavi's "Design of Analog CMOS Integrated Circuits" page 39. Btw, MIMCAPs ca be placed over active devices and therefore might not be as much
In old CMOS processes, where the square law was a good approximation, vdsat should indeed be equal to vgs-vth when the transistor is in strong inversion and channel modulation can be ignored (long L). In your case the transistor is in moderate inversion as vgs is almost equal to vth. Try to make vgs a little higher and then re-check vdsat. (...)
Hi all, When operating in saturation, subthreshold, or weak inversion, which MOSFET type has lower flicker noise: enhancement-mode or depletion-mode? Intuitively, the depletion FET should have lower flicker noise because the E-field within the gate oxide pushes carriers away from interfacial traps at the surface. Is there any data or other solid
Anything with a depletion region on either side of it will be voltage dependent. MOS channels swing from accumulation through depletion to inversion. Cgs follows gate voltage directly; Cgd, only when the channel is well lit near the drain (linear region - when it goes constant current the capacitance is sort of stood off from the (...)
Hello, As i read in the Gray Meyer's book, the drain current of MOSFET in weak inversion region is constant with different Vds. But when i simulated the operation of MOS in Cadence, the results show that the drain current is also change with Vds as in the strong inversion. Can anyone explain for me why? Does Cadence neglect the weak (...)
hai all... what do you mean by temperature inversion and how the threshold voltage gets decreased by increasing in the temperature?? tanQ
The Nwell acts sort of like a JFET gate, fighting the P inversion channel. More commonly it's referred to as body effect and considered as a shift in VT, but the JFET concept might be a more agreeable visualization. It's the relation of well to source potential that the remarks refer to. A transistor operated at (say) VB=VS=vdd has the same VTeff
lets consider NMOS. In accumulation your gate voltage should be lower than source potential - so the holes are attracted to the gate and so the capacitor is created between the poly of the gate, positive charge in channel which are divided by oxide. Co that is why the capacitance value is the same as in strong inversion - where instead of holes the
Hello, So I've read that the body effect increases VT by virtue of VSB > 0. This pulls more -ive ions into the channel. This increases the amt of gate charge needed to mirror these -ive ions prior to an inversion layer forming. This increase in the amt of gate charge translates to an increase in VT. However, what about the dependance of VT
New methods, other than using longer than minimum channel length, and strong inversion operation mode?
I read in article that "At short channel lengths the halo doping of the source overlaps that of the drain, increasing the average channel doping concentration, and thus increasing the threshold voltage. This increased threshold voltage requires a larger gate voltage for channel inversion. However, as (...)
I read that in an n-mosfet, when drain voltage is increased above threshold (in saturation mode) the inversion channel between the source and drain is pinched-off near the drain region. so the channel length decreases and so its resistance. so larger current flows through the channel. My doubt is, when a smaller portion is (...)
channel length modulation (CLM) strongly depends on channel length itself, on Vds and on inversion operation mode, hence should be extracted at an appropriate operation point. On absence of other conflicting effects which may also affect the gradient of the Id-vs-Vds characteristic (DIBL, hot electron injection), the CLM parameter λ (...)
The channel is what connects gate plate capacitance to the drain (and source). When the channel goes away only the overlap & fringing capacitance is "hooked up", the rest is returned to body instead of the inversion sheet when not inverted.
For high speed / RF, you want many narrow fingers to hold down Rg. For analog you want wider, as much mismatch (esp at weak inversion) can come from the channel edge (bird's beak) or strain effects (STI). Your foundry may or may not break down mismatch into area, w, l dependencies (often only area is discussed; whether this is because the others d