# Homework Help: Diode circuit

1. Oct 29, 2012

### luigihs

Approx what is the maximum value of Vout

I dont have any idea Im just guessing but theres not enough details I think is 0 V but Im not sure.. how am I suppose to answer this??

2. Oct 29, 2012

### aralbrec

They want the maximum output voltage, which applies to all possible input values.

3. Oct 29, 2012

### luigihs

I dont understand is that 5V?

4. Oct 29, 2012

### aralbrec

Grab Vo, what if you try to force a voltage on it. (The actual forcing could be done by a source connected to Vin)

5. Oct 29, 2012

### luigihs

The output voltage is limited to a minimum of 5V. ?

6. Oct 29, 2012

### aralbrec

You mean a maximum of 5V. If you go higher the diode turns on and there is a short to a voltage source that pins the voltage. Is there a diode drop involved?

7. Oct 29, 2012

### luigihs

Ok so is maximum ?

8. Oct 29, 2012

### SunnyBoyNY

You can try different voltage values at the output and see how the circuit behaves.

If the diode is not ideal, then there is no theoretical limit on the output voltage due to limited positive-biased diode impedance. However, I assume that the diode is ideal and thus is positively-biased and turns once the output voltage exceeds the cathode voltage.

9. Oct 30, 2012

### CWatters

Does this make it any easier to understand. It's the same circuit. If Vin >> 5V the diode conducts and stops Vout going any higher.

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10. Oct 30, 2012

### luigihs

so that means it could be 5.7 V? or more

11. Oct 30, 2012

### CWatters

No, it means it can't be more than 5.7V (=5V+Vf).

If Vin >> 5V current flows from Vin, through the resistor, through the diode to the +5V rail.