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Overdrive Voltage ???? please help me

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pelo

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overdrive voltage

Hi,
i have to design a Folded cascode OTA and i want to know what overdrive voltage i have to choise for NMOS and for PMOS.

Vcc = 5v
Ibias=1mA

Other question, for a suplly voltage of 5V what input and output swing i have to take???

Thanx by advance!
 

overdrive voltage 0.1

Hey..

Find out DC operrating point of OTA..take Common mode Voltage (for you its 2.5v) and dc simulation...

Input swing depends on what type of Differential pair u use and try to know what type of output swing u need ..i mean do u need rail torail ?

start tlike this then u 'll come near to ur goal..

best regards
 

overdrive voltage for pmos

I think the overdrive voltage is mainly dependented by the Vth and the transistor where it is used. I think 10-30% of Vth is good for current mirrors and 8-20% for cascode transistors.
 

overdrive voltage 5v

First Vov will not precisely predict the performance of circuit in short channel.

Now circuit designers use Gm/Id or Vdsat intead of Vov.

Big Vdsat will be good for matching.
Small Vdsat will bring big Gm/Id, and is good for power efficient.

For present design, the Vdsat is chosen below 0.2V, or 0.1V depending on your application and process.
 

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    pelo

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overdrive voltage should be greater than 100mV for transistors to operate in saturation region. usually designers keep overdrive volatge around 150mV for safer side.
 

For example, in my Folded cascode, my input pair is a PMOS, i have to take Vov =0.15 (0.2) for all the transistors? for the input pair, the current mirror and the cascode??

And, with a folded cascode what is the best output swing i sould take?
For Vcc = 5V,??
For Vcc = 1.6??

Thanks
 

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