Equivalent dimensions of series parallel transistors

I understand that when two transistors W/L=2/1 are connected in series then they act like a transistor of size 2/2. But what would happen if I connect two transistors in series, first one being 2/1 and second one being 2/2. What is the equivalent dimension in this case?

This makes no sense. You can't directly connect transistors in series or parallel. What do you mean by W/L ? Why would dimensions matter? Are you confusing transistors and resistors?

Brian.

seamoss said:

I understand that when two transistors W/L=2/1 are connected in series then they act like a transistor of size 2/2. But what would happen if I connect two transistors in series, first one being 2/1 and second one being 2/2. What is the equivalent dimension in this case?

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Hi, Search for "Self Cascode" to get some papers describing transistors in series. The effective length would still increase. And it has some other properties and applications too.
One such presentation is : **broken link removed**

betwixt said:

This makes no sense. You can't directly connect transistors in series or parallel. What do you mean by W/L ? Why would dimensions matter? Are you confusing transistors and resistors?

Brian.

Click to expand...

Series transistors would be with the gates connected together and the sources connected to the drains. Like this :



Parallel would be like sorces shorted, drains shorted and gates shorted. Like this :


Dimensions would matter.

OK, so this is in the wrong forum. Sorry for my comment.

Brian.

nitishn5 said:

Series transistors would be with the gates connected together and the sources connected to the drains. Like this :
View attachment 99680

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One remark - equivallent circuit for series connected transistors to obtain N times longer transistor should have the same bulk potential.

In self cascode a threshold voltages of mosfets should be different to achieve both devices in saturation for proper dc OPs.