Changing job..............

Your apprehension is well-founded. You want to leave yet do not want to burn any bridges. It's normal. Your best bet would be to be truthful and professional about your reasons of leaving. Do cite your reasons that you would like a chance to work in a larger company in order to gain more experience and exposure as compared to more money, though that may be true. Do let your boss know that such opportunities are rare and will help your own career development. Your boss might ask you to stay a little longer in order to wrap up your things. If you can afford the wait, then go ahead and take it as repaying him/her back for giving you the opportunity so far. All the best!

First of all, you're so blessed to have a job. Here in our country in Philippines, getting a job is really hard. Most of the graduates are unemployed here. Anyway, If I were you, you have to submit resignation letter. Somehow your boss will be mad / hurt ( a normal reaction )as soon he reads your resignation letter but eventually he will understand you.