Digibeta

Hello all!
I'm a cinematography student and have just been reading information about SD and HD cameras. I had a question I was hoping you could help me with.
I understand that standard definition cameras have 4:3 chips and the 4:3 chip will stretch the frame to make it look 16:9, therefore losing quality.
I read that a digibeta camera has a 16:9 chip and it can record wide screen that squashes the image to 4:3. I was wondering how can it have a 16:9 chip when it is an SD camera? It really confused me!
Can any one help explain this in layman's terms please!

I would really appreciate it. Thank you.
Vincent