Present simple passive:
am / is / are + voltooid deelwoord (past participle)John never takes the dog for a walk -> The dog is never taken for a walk.
Present continuous passive: am / is / are + being + voltooid deelwoord
I am writing an interesting essay -> An interesting essay is being written.
Present perfect passive: have / has + been + voltooid deelwoord
Our teacher has made a mistake -> A mistake has been made by our teacher.