Active Voice & passive Voice

Present:
Sam writes a letter.(active)

A letter is written by Sam.(passive)

Past:
Sam wrote a letter.

A letter was written by Sam.

Feature:
Sam will write a letter.

A letter will be written by Sam.

Pre.con:
Sam is writing a letter.

A letter is being written by Sam.

Past con:
Sam was writing a letter.

A letter was being written by Sam.

Present per:
Sam has written a letter.

A letter has been written by Sam.

Past per:
Sam had written a letter.

A letter had written by Sam.