# Full wave rectifier

Discussion in 'Homework Help' started by manking4211, Apr 30, 2014.

1. ### manking4211 Thread Starter New Member

Apr 30, 2014
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Question
a) Figure 1 shows a full wave rectifier. Sketch the output voltage, v(t) with the labels of peak voltage and period. Assume all the diodes in the circuit are ideal.

b) Repeat part a if the diodes D3 and D4 are replaced by R3 and R4 respectively.

c) Repeat part a if the circuit shown in figure 2 is used. Assume the offset model is used for the diode with the offset voltage of 0.7V.

figure 1

figure 2

Last edited: Apr 30, 2014

Apr 19, 2012
776
48
Hi.

3. ### anhnha Active Member

Apr 19, 2012
776
48
Last edited: Apr 30, 2014
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4. ### atferrari AAC Fanatic!

Jan 6, 2004
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OK, after re reading, I think I understood what I have to answer.

To whom should I sent my work?

Is it just a quiz? Any prize for the winner?

5. ### manking4211 Thread Starter New Member

Apr 30, 2014
15
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i have done part a and c.
but i am not sure correct or not.
can you send me your work or i upload my work here？

Apr 30, 2014
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7. ### anhnha Active Member

Apr 19, 2012
776
48

First, for part c, I think you are not completely right.
What is the output voltage as the input voltage is positive but less than 2*0.7 = 1.4V?
( 0< Vin < 1.4V)
Why Vout = 0 for the half cycle?
This is full wave rectifier and therefore, Vout should not be zero there.
How do you calculate the output voltage?
Could you upload your work with details on how you get that result?

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8. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Anhnha
Why 1.4V in part C ?? And positive voltage ?

9. ### anhnha Active Member

Apr 19, 2012
776
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I was referring to the positive half cycle. However, the same goes for negative half cycle.
For 1.4V, I think as Vin is less than the total drop voltage of two diodes, Vout will be zero.
Am I right?

10. ### Jony130 AAC Fanatic!

Feb 17, 2009
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But in part C we use this circuit

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11. ### anhnha Active Member

Apr 19, 2012
776
48
Well, sorry for the mistake. I misread the question!
So, manking's answer is not completely correct.
For -0.7V < Vin < 0V, Vout should be zero.
manking:
Could you show the input waveform along with your answer? This will make it easier to see if you are right or not.

Apr 30, 2014
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13. ### manking4211 Thread Starter New Member

Apr 30, 2014
15
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what should i sketch for part c.for 0V in first half period and 9.3V in the other period or exchange the position？？

14. ### anhnha Active Member

Apr 19, 2012
776
48
b) Repeat part a if the diodes D3 and D4 are replaced by R3 and R4 respectively.

Please see the equivalent circuit with diodes D3 and D4 replaced by R3 and R4 respectively.

Now for the positive half cycle:

1. Are diodes forward biased or reverse biased?
2. What are voltage drops across these diodes?
3. Can you calculate Vo now?

Now for the negative half cycle:

1. Are diodes forward biased or reverse biased?
2. If the diodes are reverse biased, remove them from the circuit.
3. Can you calculate Vo now?

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15. ### anhnha Active Member

Apr 19, 2012
776
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For the negative half cycle:
With -0.7 <Vi< 0, diode is OFF and Vo = 0.
With Vin< -0.7V, diode is ON and the voltage drop across diode is 0.7V.
Can you calculate Vo?

For the positive cycle, diode is OFF.
What is Vo?

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16. ### manking4211 Thread Starter New Member

Apr 30, 2014
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may i do it in this way?

17. ### anhnha Active Member

Apr 19, 2012
776
48
Yes, there is no different.

18. ### manking4211 Thread Starter New Member

Apr 30, 2014
15
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Now for the positive half cycle:
1. Are diodes forward biased or reverse biased? F.B
2. What are voltage drops across these diodes? no voltage drop
3. Can you calculate Vo now? peak Vo is 10 like sine wave

Now for the negative half cycle:
1. Are diodes forward biased or reverse biased? R.B
2. What are voltage drops across these diodes? any voltage drop
3. Can you calculate Vo now? 0V

is it look like this??

19. ### anhnha Active Member

Apr 19, 2012
776
48

1. Are diodes forward biased or reverse biased?
2. If the diodes are reverse biased, remove them from the circuit.
3. Can you calculate Vo now?

20. ### manking4211 Thread Starter New Member

Apr 30, 2014
15
0
1. they are reverse biased
2. R =R3+R6+R4=22ohm
3. I DONT KNOW HOW TO DO USING V=IR