[SOLVED] Comparator - cross coupled load

[kenambo]

Hi everyone,

i have attached a comparator circuit.

In which we employed a cross-coupled structure to make faster switching....

But wats the advantage of using this cross coupled load and ordinary diode connected load..

and whats the use of diode connected load which is in parallel to the Cross coupled load..?

Please refer this...

thx in advance...

 

[Dominik Przyborowski]

This cross-coupled load produce positive feedback which increasing speed (if w/l of cross-coupled fets are smaller than w/l of diodes) or provide histeresis if this fets are larger thane diodes.

 

[kenambo]

So the diodes are used for Hysterisis purpose and cross coupled pair is used for +ve feedback...
am i right?
Thanks for the help..

 

[Dominik Przyborowski]

So the diodes are used for Hysterisis purpose and cross coupled pair is used for +ve feedback...
am i right?

Not really...
In the simplest case your load is made by diode conected mosfets. In this case You haven't any histeresis. After adding cross-coupled fets You provide positive feedback and now a two cases exists:
1. if W/L of cross-coupled fets are smaller than diode connected ones, a positive feedback increasing speed of your comparator by decreasing effective resistance of output nodes
2. if W/L of cross-coupled fets are higher than diode connected ones, positive feedback provides hysteresis.

So cross-coupled fets adding postive feedback resulting with higher speed OR hysteresis.

 

[kenambo]

Thanks for ur reply.... i hope i understood this with ur help....