## mitxstudent 3 years ago This problem studies such effects and how a Zener diode may be used to ameliorate the problem. Assume that VI=13.5V, RIN=1 kΩ, and vi=55.0mV. how do i workout the value of vo

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1. morpheous87

Hi, this worked for me - vo=vin/Rin *(RD*RL)/(RD+RL) so Try this values for both vo : 0.055/1000* (1*2000)/(2001) So for both RL 2k and 4k you should have ~ 0.000055

2. mitxstudent

how do i work out rd sorry

3. nick67

did you check here: http://openstudy.com/study#/updates/5062c622e4b0da5168bd6c57 it's quite similar

4. mitxstudent

i did but there wasnt a visible formula i could use

5. morpheous87

RD should be 1, value taken from the graphic. Did my answers were correct?

6. nick67

noise value is: vo = vi*Rz/(Rz+Rin), where Rz is 1 Ohm

7. mitxstudent

0.000055 was right for 4k but not 2k

8. nick67

the noise output with zener is quite not dependent by the load

9. nick67

as far as the Rload is much higher than Zener resistance, load contribution to vo calculation is negligible

10. morpheous87

hmmm it should be almost the same, try close values :0.000054, 0.000056 should be fine

11. mitxstudent

iv attached a print screen so you can see if i have done summit wrong

12. nick67

I was talking about values with Zener in

13. nick67

with RL 2K vo about 54.92 uV, with RL 4K vo about 54.93 uV

14. morpheous87

oooohh this is the first part, where there isn't zener. The formula is a bit different here. Try these values: for 2k - 0.037 and for 4k 0.044 is it ok?

15. mitxstudent

yes you both are life savers i was stuck on this for the past 9 hours one last question is how do we work out the minimum rl

16. nick67

without Zener, vo is 36.67 mV for RL = 2k and 44 mV for RL = 4K

17. morpheous87

The formula for RL is : Vin*RL/(RL+Rin)>=5V

18. morpheous87

Try 580-590 value, ok?

19. mitxstudent

thank you for the help mate best respone and this has probably helped alot of others that have been stuck on this one

20. morpheous87

so it's everything ok now?

21. wuzupdawg

uhhhh how did you find V0 (capital V)

22. morpheous87

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