Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Maximum current in CMOS

Not open for further replies.


Junior Member level 2
Jan 28, 2012
Reaction score
Trophy points
Activity points

I have a fundamental question (might be dumb). I know square law relates current to W/L and overdrive. But is there any thing that limits the maximum current that can pass through a transistor. For example I can pass 10uA through the transistor with say a W/L = 5u/1u , can I pass 100mA through the same transistor. How the find the maximum current the channel can handle? Please assist


every transistor has limit in current and you can't pass current more than that limit.

You should find a 'saturation current' in the process specification document.


Long term, your limit may be current density in the 1st level
interconnect, which tends to be thin and minimum-width as
well as being compromised by contact step coverage. Less
than 1mA/um of width is almost certain. If you come out the
sides, like between gate stripes, that's a problem.

Behind that you have thermal concerns, how far can you
raise the intra-device temperature before you cause some
enhanced dielectric wearout, dopant migration, etc.? The
rated operating temp will be well below this, limited by
the practicalities of qualification at extreme temps and
the limited interest of markets, in it.

Then you have the simple MOSFET channel "strength",
which imposes a minimum on-resistance which, with
your rated or actual gate oxide breakdown, sets a
current (Vgs=Vds=max)/Rds(Vds=max). Though at
an even higher voltage you could punch through and
pull plenty more current, we'll assume that you have
an interest in the second attempt looking kind of like
the first and are looking to stay out of destructive
and reliability-compromising regions of operation.

Of course if that were not true, there is plenty of
opportunity to get large currents by applying large

Besides considerations above, an additional limit for max current is thermal effect.
Except gate breakdown, many damages in transistor are found to be overheat damage.

OK can i ask how i can calculate the max current that can flow through the CMOS TR ?...... please help
thanks in advance

- - - Updated - - -

OK can i ask how i can calculate the max current that can flow through the CMOS TR ?...... please help
thanks in advance

You can always ask :) This is, however, something that you'd better simulate on an extracted layout.


Not open for further replies.

Part and Inventory Search

Welcome to