smaller Length of transistor -> lower threshold voltage ?

Dear all,

I want to construct the low voltage circuit. Actually, is smaller "Length" of the transistor, the threshold voltage will lower. Or, this is not true? WHY? Could anyone answer me?

I'm very thankful for your helping.

Best Regards,

wccheng

Well if your intention is to design a low voltage circuit, then you have to do other things than just the length. The Vt of a transistor is a strong function of its substrate to source voltage. So by by reducing VSB ie making the bulk more positive than the source you can reduce the Vt. But you need to be careful because usually substrates are tied to gnd by default. For low voltage applications there are a lot of other bias circuits, amplifiers which do not consume as much head room, in literature. It would be easier to help if you said what circuit you were trying to build

Actually, is there any relaltionship between the length of the transistor and the threshold voltage? Is smaller Length of the transistor could give out the lower threshold voltage? Actually, WHY?
Thanks

Dear all,

I don't know my this explanation is correct or not. I hope anyone could comment it.

I think even the length of the transistor is decreasing, the threshold voltage of the transistor will not decrease too. It is because the threshold voltage is due to the fabrication process.

However, as the length of the transistor decrease, we could use lower Vds in order to make the transistor in saturation. Therefore, the shorter length of the transistor is favourable for the low voltage circuit design. Am I right?

Best Regards,

wccheng

the threshold voltage does decrease with channel length

if you have real player watch lectures from

https://www.edaboard.com/ftopic80119.html

Dear v_naren,

Could you tell me which lecture lesson is correct?

Best Regards,

wccheng

http://www-inst.eecs.berkeley.edu/~e.../Lectures.html

Dear v_naren,

I am extermely thankful for your helping. :)

Best Regards,

wccheng