Plotting Bode of Resistor w/ DC Source: 20*log(0)

[ujjval rathod]

I am ploting bode of resistor connected with DC source.So no freqvancy at all! The bode magnitude plot should be(or it
should start from) 20*log(jw)=20*log(0) (jw=0 because we have dc source) what should be the value??for step of 5v... what
should bode look like??

 

[anorlunda]

I am ploting bode of resistor connected with DC source.So no freqvancy at all! The bode magnitude plot should be(or it
should start from) 20*log(jw)=20*log(0) (jw=0 because we have dc source) what should be the value??for step of 5v... what
should bode look like??

Maybe it would look like a point. I really don't know because Bode plots are not intended for DC.

Why are you doing that?

 

[ujjval rathod]

yes true bodes are not for DC... But can you tell me what is the frequency of DC I mean 0 or Infinity?

Or suppose I have square wave of some frequency...then what would be the transfer function?? for R it would be L^-1(r)=1 or r and for input i think it should be 1/s...

 

[ujjval rathod]

also if you can tell me...this..

If we have LTI system and if we apply one frequency say 5HZ the in output will we get same frequency or we may get different
frequency?? yes amplitude and phase may change that i undestand..

 

[anorlunda]

yes true bodes are not for DC... But can you tell me what is the frequency of DC I mean 0 or Infinity?

Or suppose I have square wave of some frequency...then what would be the transfer function?? for R it would be L^-1(r)=1 or r and for input i think it should be 1/s...

The frequency of DC is zero. A square wave cane be represented as a Forier sum of many frequencies. Google Fourier series.

 

[ujjval rathod]

ok i know Fourier series... So you mean we have to get Fourier series of the signal and then once we get it... we take laplace transform of that...?? So that we can analyse bode...

 

[anorlunda]

ok i know Fourier series... So you mean we have to get Fourier series of the signal and then once we get it... we take laplace transform of that...?? So that we can analyse bode...

That is still not appropriate for Bode plots. A Bode plot shows the response of a system as a function of frequency. Continuous changes in frequency.

A Fourier series of a square wave gives you values at discrete integer multiples of the fundamental frequency. When plotted, you would have a series of isolated points, not lines.

Once you have a specific signal, it doesn't make sense to make a Bode plot of it. Perhaps you are thinking of power spectral density.

 

[ujjval rathod]

I am thinking of circuit which has only Resistance and a supply...so Laplace of resistance of 1ohm is always 1 so we only need to take laplace of input to analyse a bode...

 

[ujjval rathod]

hey i am stuck with the question of bode of circuit having resistance connected to sinusoidal source...

What i am trying to get is bode of that circuit... so I take laplace of sin=1/(s^2+1)... Now this is our T.f. If i put diffrent values of frequency do i get the bode magnitude plot??

 

[FactChecker]

If your circuit has an input location and an output location, then it has a Bode plot. Otherwise, it doesn't. An input location assumes that you can inject any frequency at that point.

 

[ujjval rathod]

that's ok! My input is Sin wave(Vin) and output is voltage across R(vout)...

 

[anorlunda]

A voltage source connected to a resistor has the input terminals and output terminals at the same place. Your transfer function is 1 no matter what the voltage and no matter what the resistance.. A bode plot of 1 is a horizontal line of magnitude 1 for all frequencies. That's pointless.

I think you have some conceptual problems about transfer functions, circuits, and Bode plots.

Can you tell us what you are trying to accomplish?

 

[ujjval rathod]

you are right! I understood the things now... sorry for some silly questions that mess you up!
Thanks for reply.