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# [SOLVED]subtreshold leakage and supply voltage

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#### farzaneh_2561

##### Member level 1
Hi there,
I have a question, How does subtreshold leakage change with Supply Voltage and also technology?
Thanks

#### Prashanthanilm

##### Full Member level 5
Sub threshold leakage is basically the leakage when the gate voltage is less than threshold voltage.

So, when the supply is less than Vt , we dont expect any current. But, due to charges there is a possibility of current flow from Source to drain and we term it as Sub threshold leakage

Technology :
If the library is Low Vt then the sub threshold effect will be more compared to HVT library.

farzaneh_2561

### farzaneh_2561

Points: 2

#### farzaneh_2561

##### Member level 1
Thanks for the reply. I'm familiar with the concept. I guess I didn't describe my question very well. If we lower the VDD (but not under the threshold voltage) does it affect subthreshold voltage?

#### Prashanthanilm

##### Full Member level 5
Yes, I hope you are talking about the drain voltage variation.
If the Drain voltage is more, more Diffussion area will be present in Drain region and hence more leakage.

Eg : Vdrain = 5V will have more leakage than Vdrain = 3V keeping Vt=1V .

farzaneh_2561

### farzaneh_2561

Points: 2

#### saurabhr8here

##### Member level 3
$Ids=Is\frac{W}{L}{e}^{\frac{Vgs}{Vt}}(1-{e}^{\frac{-Vds}{Vt}}+\frac{Vds}{Va})$

Use this equation to estimate how threshold voltage varies with supply voltage.

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