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How to change the swing of a signal?

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husseinadel

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hello

i want to change the swing of a signal from 0 -->1.8 to 0 -->3.3,,i tried using nmos transistor as a switch putting the signal on its source,,1.8 bias on its gate and 3.3 supply to the drain through resistance,,taking output from the drain,,it works well but when i decrease the frequency,,it didnt work well,,,note that i am operate at 1 Gbps,,can anyone suggest me a way to change the swing or even tell me the drawbacks of what i mentioned above....thanks
 

changing the swing

it seems a problem for ur circuit. when the source voltage is 0, the NMOS is turned on, there is a current flow through the resistor and NMOS transistor, the output voltage is dependant on the resistor ratio. so the resistor should be large. It is not easy to work at the high frequency
 

Re: changing the swing

pfd001 said:
it seems a problem for ur circuit. when the source voltage is 0, the NMOS is turned on, there is a current flow through the resistor and NMOS transistor, the output voltage is dependant on the resistor ratio. so the resistor should be large. It is not easy to work at the high frequency
Click to expand...

i took care ,,i made the resistor value approx. large enough to have most of the drop so that Vout(low) approx. equal 0.3 and i accept it for my application,,,nmos enter the triode this may be the limitation on speed but as i said itt works with me at 2Gbps ,and its performance degrades when decrease frequency to 1 Gbps

thanks
 

changing the swing

at high freq. the parasitic caps start to be dominant , and therefore the equivelant resistance decrease if u want to make the speed OK, u may furthur increase the resistance to make the caps dominant early, since the shifter seems to work at high freq. only.
 

Re: changing the swing

Assalamo alaykom :)

I think that you can do it using a buffer consists of two cascaded high speed inverters (but that depends on the allowed area available to you in you layout restrictions)...
When making that buffer, your aim is to get sharp characterestics to be fast enough..

And notice that it will act as if your input to inverter is nosy (i.e. has weak one's) by proper choice of noise margines, you'll solve it..

I hope that helps.

Salaam :)
Ahmad,
 

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