Can i design a simple PWM modulator without using opamp or 555 ( use only bjt). Please help

 

Yes a transistor multivibrator,...

 

Welcome to AAC. This is a forum for discussion about electronics and other things somewhat related. It is not a place to ask others to engineer a circuit for your needs. We will happily instruct you on how to but we will not do it for you. As Dave said, yes, you can use transistors to develop a multivibrator circuit. If you don't know how to do that then it is suggested you research it. Learning about electronics is the best thing you can do for yourself. Leaning on others knowledge for answers is OK as long as you are putting forth the effort. Some of us here are quite experienced and will have outstanding advice. Me? I'm not so savvy on such things as I'm pretty much a beginner too. However, I've gotten lots of advice regarding my proposed solutions for issues I've attempted to solve. The people here are more than happy to help. We're just not interested in being an engineering services group.

If you're curious about the possibilities - it's always OK to ask. Even OK to ask what you might think is a dumb question. The only true "Dumb" question is the one nobody wants to ask. THAT is dumb. Ask. We'll help where and when we can. The second thing we ask is that you be clear about your needs, purpose and intentions. The more information you can provide the better we can help you.

Again, welcome to the forum.

 

As for your needs, a 555 is already a good stepping stone for a simple PWM. To do it with other components is to literally reinvent the 555. And it can be done pretty much without an opamp.

Check out this link: https://www.electroschematics.com/pulse-generator-with-555/