Silicon Diode = 0.7V

 

hi jjb,
Welcome to AAC.
As this is homework, please post your best attempt at answering, we can then help.
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Hi Eric,

Thanks for the response. So far I had assumed Ir=V/R. Therefore potentially 0.7/510 = 0.0013. However, to my understanding this is incorrect. Thus not being able to work out (a) (ii) I sadly cannot attempt to complete the other questions.

Thanks

 

hi jj,
OK,
Consider this part, You should know a diode conducts in one direction and blocks current in the opposite direction
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The current will flow through the path of least resistance which could result in fusing the circuit?

 

Come on jj a fellow Yorkshire man can do better than that...

Consider the Diodes a form of Logic Gate.

You don't want either switch to operate both the circuit paths..

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result in an open circuit? Slightly confused by the last comment

 

hi jj,
Look at this edited drawing, L1 and L2 are 5v lamps,
Consider what the switch action for the lamps would be with and without the diodes.??
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the current would not reach the lamps?

 

hi jj,
Look at these 3 images.
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BTW: Can you say which course and year you are in.? help us to give better answers.

 

Thanks for the images and help - all very much appreciated. Apologies I am pretty useless at this - I am trying to catch up 2/3 years worth of physics within a few weeks before an exam in 2 days. I study MME (Music, multimedia and Electronics) and am in 1st year.

 

OK, so do you now understand the action and purpose of those diodes.?
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I believe so, I understand that diodes either cause or prevent current from flowing and if I'm not mistaken if they were replaced by a short circuit in this case this would lead to an open circuit and current not being able to flow throughout is that not correct??

Once again, Thanks for all of your help Eric

 

hi jj,
Think of diode as a switch that will only allow current flow thru it in one way [ in the direction of the 'arrow'] and not in the opposite direction.

What is the next step in the questions.?
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What would go wrong? = in the case of the homework; Q1 would not get turned on?

 

No,
look at the image 285c , both lamps ON, . and Gate to 0V, ,, Source to +5v

Don't forget its a P type FET

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Oh yes I meant to say that - so both lamps are on? Would they take up too much current and so the transistor won't function...? I'm sorry but I'm still not quite sure what would go wrong.

 

hi jj,
Its the definition of wrong thats misleading.
It should say what would be the effect on the circuit operation, if the diodes were removed/ shorted out

Consider the just the switches and the 'R' resistor.

The switches are connected as an OR gate, either one ON would connect the Gate to 0V and turn on the P FET.
BUT
the logic inside the U1 unit would not know which switch has been switched ON, as either switch would pull both logic lines Low.

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I think you are going to have a problem with this Course, catch up.

 

Yes I do see what you mean.

Thank you for all your help Eric, even though it may have caused the both of us a little frustration.

'think' maybe an understatement as I am fully aware of my lack of knowledge on the module but I shall nevertheless prevail in attempting to understand the world of circuit analysis and design.

Many Thanks for your guidance and truthful advice. Any further tips would be much appreciated.

p.s I would be curious as to what you do for a living/ area of speciality is?

 

hi jj,
Try to tackle the remainder of those questions, come back if you have a problem.
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OT:
Moved from West Riding Yorkshire about 50 years ago to Sunny Portsmouth.
Retired C Eng;;
https://en.wikipedia.org/wiki/Chartered_Engineer_(UK)