MOS differential amplifier design

[zsabre81]

Hi, i'm new at this forum, I'm an EE student (senior standing and not very bright). Anyway, I'm currently working in design project where I have to design a MOS differential amplifier. I have attached the design requirement info in a *.zip file (its actually a pdf file but since the forum doesn't allow it...i zipped the pdf files). I really don't know where and how to start in this project and thus very desperate too :cry: . So any help or suggestion on how to approach this design or what to start first? Or even better maybe a general step by step procedure (which is great if possible). TA? well i do have a TA but apparently he's not very helpful either, he's response often ," i can't help on your question since its like giving away the answer?" (i interpreted it as simply his way of saying "I don't know"). Professor? well given the level on how far i'm into this project, i don't think he's gonna be very pleased, and there're other 32 students in my class who come to him (who are much smarter than me) so i'd figure i won't have that much time to spend with him. Well anyway.... anyhelp would be gretly appreciated. Thank you very much ^_^

 

[Optikon]

You should check your text for an analysis and modeling of a transistor version of an op amp, that wil help. Essentially what you need is an input stage (make a differential pair using FETS since you need to use MOS), make a gain stage and make a simple output stage. For the output stage, I would recommend a simple push-pull type. If you desing a basic input stage, you will easily meet the criteria for the Rin. Your gain stage can be designed to meet the AV spec and just about any active-type output stage will get you much less than 1Kout Rout (If you use MOS here, dont include any resistors just push-pull with N & P types)

The gain that is referred to (4000 differential mode), refers to the input being 50uV and your output in open loop fashion. Try a basic design and see how it performs, you should be able to meet the given specs quite easily.

 

[zsabre81]

push and pull type?

 

[Optikon]

push and pull type?

Check your text for class AB amplifiers.. A push pull output stage is similar in design.