Exam-style question
Try this first
Which of the following is a correct statement about the duty cycle of an astable 555 timer?.
- A.It is always 50 %
- B.It can be adjusted by changing R1 only
- C.It can be adjusted by changing R2 only
- D.It can be adjusted by changing both R1 and R2
Model answer
What a good answer should say
- It can be adjusted by changing both R1 and R2
Explanation
Why this works
Rule: Duty cycle D = (R1+R2)/(R1+2R2). Both resistors influence the ratio, so changing either one or both will alter the duty cycle.
Conclusion: Both R1 and R2 can be used to adjust the duty cycle.
Common mistake
No common mistake is linked to this question yet.