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[SI-LIST] Re: simulating Mos in series
- From: super cop <super_uvais@xxxxxxxxxxx>
- To: parthsv@xxxxxxxxx, super_cop@xxxxxxxxxxxxxx
- Date: Fri, 7 Mar 2003 00:57:49 +0000 (GMT)
Hi Sampath,
Thanks a lot for breifing about the same !!!
But why does it act like that, or what tells it to
change the terminals while simulating.
A pass transistor is a simple , single tranisitor or
like here m1 and m2 , m3 in series form a pass
transisor ?
Apologises for keeping on asking such dump
questions.
Regards.
--- Parthasarathy Sampath <parthsv@xxxxxxxxx> wrote:
>
> Hi,
> From your netlist, I can understand one thing.
> You
> have given power supply to source of M1, followed by
> M2, and M3.
> Remember Drain and source in MOS can always be
> interchanged and this is one important concept to be
> taken into account in Pass transistors.
> I belive this is what is happening.
> So while you have connected 5v to source to M1, it
> acts as drain pushing it into saturation and you see
> a
> vt drop on it. Further down m2 and m3 are in linear
> region and nearly 0v across source-drain( viewing
> from
> bottom) and same voltage from x is passed onto
> pointb.
> Hope this clears.
> Regards
> Partha!
>
> --- super cop <super_cop@xxxxxxxxxxxxxx> wrote:
> >
> > Hi All,
> >
> > I am trying to simulate the behaviour of Series
> > connection of Mos
> > and analyse the max & min voltage the connection
> can
> > pass from i/p
> > to o/p.
> > although i am able to see the results as in book,
> i
> > ma not able
> > to understand the concept or to say i am getting
> > confused. let me
> > explain.
> >
> > ***** checking with n-mos connected in series
> > m1 x in pointa 0 n l=1u w=5u
> > m2 y in x 0 n l=1u w=5u
> > m3 pointb in y 0 n l=1u w=5u
> > .model n nmos level=1 vto=0.7 kp=110u gamma=0.4
> > lambda=0.04
> > phi=0.7
> > .op
> > vin in 0 5
> > vdd vdd 0 5
> > vpointa pointa 0 dc 5
> > .end
> >
> > If run, this shows voltage at node pointb to be
> of
> > Vdd-thn
> > (3.786) i.e max transfered from pointa (5v).
> below
> > is operating
> > point information.
> > Where i am confused is : when vgs of m1 =0 i.e
> less
> > than vthn,
> > won't be m1 in cut-off region since ids =0 when
> vgs<
> > vthn.
> > But it shows saturation region.
> >
> > ***** operating point status is all
> simulation
> > time is
> > 0.
> > node =voltage node =voltage
> > node
> > =voltage
> >
> > +0:in = 5.0000 0:pointa = 5.0000
> > 0:pointb =
> > 3.7867
> > +0:vdd = 5.0000 0:x = 3.7868 0:y
>
> > =
> > 3.7868
> >
> > **** mosfets
> >
> > subckt
> > element 0:m1 0:m2 0:m3
> > model 0:n 0:n 0:n
> > region Saturati Linear Linear
> > id -112.6738p 101.8893f -11.4548p
> > ibs -50.0000f -37.8676f -37.8676f
> > ibd -37.8676f -37.8676f -37.8673f
> > vgs 0. 1.2132 1.2132
> > vds -1.2132 296.4245n -32.3396u
> > vbs -5.0000 -3.7868 -3.7868
> > vth 1.2126 1.2126 1.2126
> > vdsat 625.1077u 296.4245n 32.3396u
> > beta 576.6913u 550.0000u 550.0007u
> > gam eff 400.0000m 400.0000m 400.0000m
> > gm 360.4942n 163.0335p 17.7868n
> > gds 4.2984p 343.6462n 345.3111n
> > gmb 34.0378n 15.3936p 1.6794n
> > cdtot 1.1511f 139.9684a 196.3270a
> > cgtot 1.2983f 480.4520a 480.7869a
> > cstot 2.7930a 196.0400a 140.2611a
> > cbtot 144.4435a 144.4435a 144.1988a
> > cgs 2.7930a 196.0400a 140.2611a
> > cgd 1.1511f 139.9684a 196.3270a
> >
> >
> > How to calculate drain voltage when you know gate
> > voltage & source
> > voltage forehand. I understand this one's a
> dump
> > one to ask ,
> > but i need to . Hope this one's does not
> intrigate
> > any one.
> > Thanks in advance for all the help .
> >
> > Best regards.
> >
> >
> >
> >
> >
> >
>
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