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What happens to current flow in mosfet when temperature decreases?

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vreddy

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wat happens to current flow in mosfet when temperature decreases??

can anyone elaborate it.?/
 

Re: MOSFET

the dependence of Id on temperature is negative and hence when there is a increase in the temperature the current increases and vice versa.... this is why mosfets do not suffer from thermal run away.....
 

Re: MOSFET

It is there in the explanation of the model :

In weak inversion: Id=Im * exp( (Vgs-Vm)/n*φt)*[(1-exp(-Vds/φt), where Im=(W/L)*I'm
φt=(k*T)/q
In saturation: Id=(k/2)*(Vgs-Vt)²
Vt=Vto+γ(√Vsb+φo -√φo)

so doing the math we find out that the dependance from the factor of the temperature is a bit complecated.

According to Tsividis analysis, the dependance on the temperature in strong inversionhas as follows: a temp increase tends to increase the drain current for low currents and vise versa for high current. The effective mobility is decreasing with temperature but always depends on the current : high or low.

D.


D.

D.
 

Re: MOSFET

there are so many effects with temperature
With increase in temperature
!)threshold voltage decreases..as a effect leakage current(when the transistor is off) increases....in brief off current increase ..on current decreses


For example
if suppose threshold voltage is 1 v..if temp has increased then thres volt decrease to 0.7 v(say)..at 0.7 transistor will be on..but actually it should be off..whatever the current which flows at that volt will be the leakage current

got it
 

Re: MOSFET

Can u specify any euquation which gives any proof for this behaviour ?
 

Re: MOSFET

eqn

Un(mobility)=T^(-M)

here M=2.7 for si electrons
m=2.5 for holes in si.

Vt(effective)=Vt-Kt(T-T0)

Kt--positive temperature constant


Un(effective) directly prortional to Vt(effective)


so As temperature is increased, Id(drain current) can be increased.


u can see this in process corner variations



regards
venkat reddy
mtech(vlsi)
 

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