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Multifinger Transistor

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ryusgnal

ryusgnal

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current density

Wide transistor usually folded to so as to reduce both S/D area and the gate resistance. The folded transistor is called multifinger transistor. if i want to fold the transistor, how to calculate the appropriate number of fingers i have to use and the width of each finger? Thanks for any reply....

Added after 1 minutes:
 

multi-finger transistor

refer to the process manual is ok.
the foundry will give some guidelines.
 

determine resistance in a multifinger transistor

ryusgnal,
process manual will tell you that what should be mininmum and maximum width of transistor, in case if we do the fingering.
Similarly In my view, no. of fingers you can take as much as your need there is no limit. But some time max. and min. no. of fingers are also given in design manual for respected technology and we can not take more than that.

If I am wrong then viewer please let me know.
Thanks!
 

finguring the transistor in vlsi

I think the main important thing the layout consideration in this issue. So, you have to think about the layout. How much finges and how much blocks you need.
And the maximum current density of the metalization is also important.
 

    ryusgnal

    ryusgnal

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multifinger transistor

The total width = # of fingers X channel width.

The number of fingers is dependent on application. For example, the total width is dependent on the target gm desired. You can then create multiple fingers in order to minimize series resistance in the gate, channel, S/D contacts.
 

I agree with the equation that krashkealoha gave. The minimum width will depend on the process and on the application you are workin on Using multifinger transistors will help you match devices better. By using multifinger you will be able to used layout techniques as interdigitation or cross coupling whenever you need matching, i.e. current mirrors, input pairs.
 

I'm Using 0.18 TSMC process for 477MHz RF Transceiver. Does anyone have any suggestion?
 

Hi,

I feel it depends on the current density you have to pass throgh each finger
 

Now, I have the same problem, but I have to make an output transistor to conduct amperes of current, but just a current pulse 2..3 ns.
 

naru.vlsi said:
Hi,

I feel it depends on the current density you have to pass throgh each finger
Click to expand...


If i need current 1.14mA pass through the fingers, what is appropriate width for each fingers?

p/s Transistor width is 371.52um and length is 0.18um. Help Please...
 

ryusgnal

The width of each finger will basically depend of what is the maximum current density for each contact in your process. I don't have access to the your process data but there should be a spec with the maximum Idc for each contact. Depending on this parameter you determine the amount of contacts you need and hence the width per finger. Typically the current density for pulsed current is higher than for dc current.
 

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