I don't see where you put all the points but the ones I see appear to be in the right places. The other points should be about on the lines so it looks right to me.
I assume that by "cut of frequency" that you are talking of "cut off frequency"This gets a bit trickier. See the following Wikipedia articles which do a better job explaining than I can.
Ephraim you still do not have this right.Your gain values for 1, 2, 4 KHz at 100K ohms (3rd column) are 100, 99.6, 99However your red lne shows a value of 100 at 1KHz (correct), about 95 at 2 KHz (wrong) and about 85 at 4 KHz (wrong). You need to plot these points first - I would like to see dots at these points. You then join up the dots with a curve, not with straight lines as you have done.I will email you a copy of your graph how I would like to see it (I will try posting it here as well, but it may be too small).You need to get this right, if I was marking you on this I'd probably fail you....Cheers // David(I have replotted the top line in bright red)
Ephraim...of the two graphs above, the first one is better. Why? because the value of the 10K gain at 32 KHz is 10, you have it down about 9. But apart from 2 and 4 KHz, I see no sign of you putting points on the graph to show your values as I did with my 3 points, and Elizabeth did with her Excel graph. You do not seem to have grasped this. Let's take 16 KHz. This will be about 2/3 of the way between 10 and 20 KHz on the bottom frequency scale. 32 KHZ will be about 1/3 of the way between 30 and 40 KHz. You don't have to be exact but you should put the points on the graph. I'll send you a full size graph in email and try to explain this.
Ephraim...I found the following tutorial on graphing which may help you.It does not have anything on how to plot the points, which seems to be the main thing that you have trouble with.But it does have some good points about other errors you have made, and it is worth watching.Cheers // David
Well that looks nice. But your points are in the wrong places after 4 KHz.... At 8 KHz your red point is at 7.5 KHz and there is no green point. At 16 KHz your red point is at about 13 KHz - should be more to the right - and there is no green point.
At 32 KHz your red point is right, but there is no green point.
Both your 64KHz points are at about 44 KHz. At 128 KHz your red point could be a little bit more to the right, but your green point is at about 80 KHz. At 256 KHz your red point is right but your green point is at about 180 KHz.Please see email just sent and see if this helps.I get the impression you plotted the lines first and then put the points on? It should be the other way round. And don't worry if your points are not exactly on the line, they may be slightly off. the line should be a "Best fit" with points above and below the line if they don't fit exactly.
Ephraim that is better , you are getting this now, but:- Your 256K points are still not right, one is at about 210K and the other about 230K- but I see you have put dots at the frequency axis to refer to, use them!- all your points from 8K up are a bit too much to the left, but not much, this is always a problem wehn getting used to Log graph paper- you still have sharp corners where your lines got from flat to downwards sloping. Elizabeth told you above to put a curve on these. Listen to her, she knows more than I do!But I'd probably pass you on that, it is fairly near to what you should have.
For each curve, note the frequency where the two straight lines meet. Calculate or measure the gain at this frequency, and plot the point on the graph paper. Note that the point's gain will be about 0.7 times the gain where the two straight lines meet. Draw the curve through this point to connect the two straight lines.
Let's stick to the blue gain-of-ten curve and points for this discussion. I forget whether you are simulating or measuring your points. I suggest you simulate or measure the gain and phase-shift at 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200 kHz, and plot these points on your graph. Do you see why I am suggesting this?What do the terms "closed-loop gain", "open-loop gain", "loop gain" mean to you?Do you know how to do a paper-and-pencil analysis of your circuit?We need to know what you understand, so we can build on that.
Hi peterthanks for the reply, i build and simulated the circuits below are the result for both the 100 and 10 kilo ohms, my next task is to graph the results and identify the cut off frequency thanks
Hi peter please look at this attachment, do i need to do the calculation and connect both the voltage and frequency respond like this?
please kindly show me a demonstration on how i can connect the two curves.
Hi NyameFor 100Kohms, simulate Vo/Vi gain at 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 kHz and plot the points.For 10Kohms, simulate Vo/vi gain at 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130 kHz and plot the points.These points will show you the curves between the straight lines.
The discussion centers on correctly drafting frequency response graphs for electronic circuits, specifically plotting gain versus frequency for different load resistances (10K and 100K ohms). Key issues addressed include accurate placement of data points on logarithmic frequency scales, proper representation of gain values at specified frequencies, and the importance of plotting points before drawing smooth curves rather than connecting points with straight lines. The concept of cutoff frequency is clarified as the frequency where the output voltage drops to approximately 70% (or -3 dB) of its low-frequency value, with references to Wikipedia articles on cutoff frequency and decibels. Participants emphasize simulating or measuring gain at multiple frequencies to obtain detailed data points, then plotting these points accurately on the graph. The need to create smooth curves that reflect the actual frequency response, avoiding sharp corners, is highlighted. Suggestions include using graph paper with logarithmic scales, marking points precisely, and understanding terms like closed-loop gain, open-loop gain, and loop gain. Tutorials and example graphs are recommended to improve graphing technique. The overall goal is to produce clear, accurate frequency response plots that correctly identify cutoff frequencies and reflect the circuit’s behavior under different loading conditions. Summary generated by the language model.
