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low dropout regulator

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Hi I made this Low drop out regulator and seems to have errors like small length and narrow width in AC analysis... I can't figure out how to fix this.. please help.. I got no problem in dc opt pt of LTSpice since I got my desired output of 800mV..
 

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Are you asking how to replace the default LTSpice NMOS and PMOS devices with ones where you can specify channel length and width and have parameters that are specific to a particular CMOS process? That is what you need to do... The ones in your simulation are not the correct ones to use for CMOS circuit design.

Start by reading the section of the Help file that deals with Monolithic FETs:

hlp.gif
 
MikeMl oh.. someone told me that also... to not use the default LTSPice NMOS and PMOS... can you please attached even one NMOS and one PMOS that is designed and not default.. I want to make it a basis .. thank you
 
MikeMl and also... is it ok if i ask a favor on how i would be able to improve my LDO because my teacher wants to have an input of around 1V-1.3V with an output of 0.8V with +/-2% accuracy and power supply rejection of 20 dB... please ..
 
Are you trying to design a regulator chip at the silicon level, or just design a regulator using existing FETs and other components?
 
MikeMl what would be easier to do?
It is much easier to design something using "off-the-self" discrete parts for which individual "data sheets" and for which "Spice models" exist.

If your assignment is to design an "integrated-circuit", you need to pick a set of "design rules" that are matched to a specific chip foundary's IC Process. The foundary usually supplies Spice model parameters that match their process. For example, here is what MOSIS says.
 
Why doesn't the teacher teach you how to design a low dropout regulator IC instead of you guessing about it and asking how to do it in an online forum?
 
MikeMl oh ok I get it now.. i will try first to do it with the default MOSFETS then try to move on with the ones (ICS) that already got the specs that is useful for.. Im just going to ask question some other time.. Thank you so much for the help
 
audioguru you answer is quite unhelpful.. Thats why im here to ask question not to have someone telling where my teacher is lacking.. Sorry if I sound rude but Im here to ask question and will be grateful if someone helped me...
 
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