Electrical Engineering Master of Science: Taking Letters of Recommendations from different departments or fields I would like to apply for Master of Science about electrical engineering, in USA. Most universities require 3 letters of recommendation and I am a little confused about from whom to get them. 

I scored a very high GPA but I did not participate in any kind of research activities. However, there are many professors that know me very well, particularly my enthusiasm, my potential, my passion to learn new things and my ability to critical think and judge the information without taking it for granted. 

I want to apply to the schools with the "electronics, semi-conductors" branch. 

However, the professors who know me well are from : 1) electrical engineering, power electronics area 2) electrical engineering, computer branch and 3) mathematics department, I took differential equations and calculus from this professor.

I want to ask the followings: 

1) Are old professors regarded more important or less important compared to younger professors ?

2) Is it OK to take letter of recommendation from a professor in another discipline or even different faculty, knowing that he will write a very good letter ?

3) Is a letter of recommendation from a famous faculty member that does not know me very well is better than a letter of recommendation from a less well-known professor that knows me very well ?

4) Is a professor that did his/her Masters or doctorate in USA regarded as more important compared to ones who did not ?
1) Are old professors regarded more important or less important compared to younger professors ?


  I cannot speak to this, but in general, a well known researcher in the
  field you are applying to is more valuable than a not as well known
  researcher. For example, Terence Tao is only 41
  (https://en.wikipedia.org/wiki/Terence_Tao), and Manjul Bhragava is only 42, (https://en.wikipedia.org/wiki/Manjul_Bhargava). Their age is considered decades younger
  than many profs in math, but I would wager any mathematician would do
  anything to get a recommendation letter from the profs I have mentioned above.


2) Is it OK to take letter of recommendation from a professor in another discipline or even different faculty, knowing that he will write a very good letter ?


  I can speak to this. I am an electrical engineer who has done a MASc. and two of my
  recommendation letter were from mathematicians, one pure and one
  applied. But then again I applied for a very mathy branch of EE. 
  
  I would not consider semiconductor research to be an extremely mathy branch of EE, (compared to research in signal processing, or control theory)
  and this is coming from another EE. In semiconductor research they
  need people with good simulation skills and will be able to write
  softwares of which the theories are grounded in PDE. You can find an
  applied mathematician who works in PDE (preferably computational PDE)
  or a physicist who will provide you a letter.


3) Is a letter of recommendation from a famous faculty member that does not know me very well is better than a letter of recommendation from a less well-known professor that knows me very well ?


  The best case scenario is that you receive a letter from someone who
  knows you very well and who have written a good letter. Otherwise, you
  need someone who knows you a little but will write a good letter. The
  last you want is someone who knows you very little and will probably
  write an average letter.


4) Is a professor that did his/her Masters or doctorate in USA regarded as more important compared to ones who did not ?


  This is an important question and I think it is highly dependent on
  the tier of school you are applying to. I can't imagine the top 5
  engineering universities will ever perceive a letter from a reputable
  researcher from overseas (outside of US or even Canada) to be less
  valuable.