Why is the rise time AKA slew rate of an amplifier used to prevent distortion of signal in a signal conditioning circuit? Thank you
Hi,Why is the rise time AKA slew rate of an amplifier used to prevent distortion of signal in a signal conditioning circuit? Thank you
Alright, thanks for the explanation.I am sure there will be help.
First, a point, this belongs in the Homework forum, but the moderators will move it so don't repost there, but for the future keep that in mind.
The general way to get homework help here is to start with what you know, and get to the point of confusion, then ask about those specific things. In this case, you should tell us what you think the answer is, and where you lose the thread of the explanation so that we can help you learn the gaps.
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Alright, here is what I know. The slope of a ramp has distortion with a flat peak (just like the slew rate waveform we see). The maximum slope of a sine wave is round, meaning the curve goes up and reaches the max point and then it goes down, or it can be the other way round.Hi,
Here is a hint.
Look at the slope of a ramp as compared to the maximum slope of a sine wave. See what you can deduce from that.
What I know about slew rate is that slew rate measures the speed that the output can move to comply with the changes in amplifier’s input. The faster the output can move, the better its compliance with input changes, and the lesser the distortion to happen. I honestly do not feel that slew rate can prevent distortion. Initially, I was thinking that slew rate is a distortion but I was told by my lecturer I was wrong, since slew rate can be in triangular waveform.I am sure there will be help.
First, a point, this belongs in the Homework forum, but the moderators will move it so don't repost there, but for the future keep that in mind.
The general way to get homework help here is to start with what you know, and get to the point of confusion, then ask about those specific things. In this case, you should tell us what you think the answer is, and where you lose the thread of the explanation so that we can help you learn the gaps.
Lots of people here want to help, so go for it.
You appear to be confusing a couple of concepts. When we speak about a "slope" we are talking about the rate at which one thing (the signal) is changing with another (time). The slope of a curve at some point is the slope of the straight line that is tangent to the curve at that point. If you've had any calculus (have you?), it is the derivative of the function at that point. So the slope may change from one point in the waveform to another, but at any given point it is just a number and a number can't be "round", so to talk about the maximum slop being round is meaningless. Think of a road going across a valley and over a mountain -- the slope is the steepness of the road at any given point and the maximum slope is just the steepness at the point where the steepness happens to be steeper than anyplace else. Would it make any sense to talk about the maximum steepness along that road being "round" or any other shape?Alright, here is what I know. The slope of a ramp has distortion with a flat peak (just like the slew rate waveform we see). The maximum slope of a sine wave is round, meaning the curve goes up and reaches the max point and then it goes down, or it can be the other way round.
Did I get the facts right? If no, may I know where did I go wrong? And what should I look for next?
Thanks
Here are my answers. Do let me know if I am wrong anywhere or where I lack of.In general terms, most of the time, you want a signal to pass thru an amplifier
with the only alteration being its magnitude.
https://en.wikipedia.org/wiki/Amplifier
So ask the question, what properties do signals have, and what do you not want
altered by the amplifier.
Regards, Dana.
yup, i have learnt derivative. With your comment of "the maximum slope is just the steepness at the point where the steepness happens to be steeper than anyplace else.", I now know the meaning of max slope. The signal changes the most per unit time at the point where the value of y at the y-axis is zero [only true is the sine wave starts at the origin (0,0)] What would happen if the amplifier generating that signal was incapable of changing as fast as the sine wave does at that point? I would say slew rate occurs. Its like the signal will try to get shortcuts to comply with the changes, which is why some rise time and fall time of the slew rate is a straight line and distortion will occur.You appear to be confusing a couple of concepts. When we speak about a "slope" we are talking about the rate at which one thing (the signal) is changing with another (time). The slope of a curve at some point is the slope of the straight line that is tangent to the curve at that point. If you've had any calculus (have you?), it is the derivative of the function at that point. So the slope may change from one point in the waveform to another, but at any given point it is just a number and a number can't be "round", so to talk about the maximum slop being round is meaningless. Think of a road going across a valley and over a mountain -- the slope is the steepness of the road at any given point and the maximum slope is just the steepness at the point where the steepness happens to be steeper than anyplace else. Would it make any sense to talk about the maximum steepness along that road being "round" or any other shape?
So draw a reasonably accurate picture of a sine wave and identify where along that wave the signal is the steepest -- where the signal changes the most per unit time. What would happen if the amplifier generating that signal was incapable of changing as fast as the sine wave does at that point?
So if I have a signal that is a pure sine wave at a frequency f and with an amplitude A and I pass it through an amplifier with a gain of K, what is the minimum slew rate that my amplifier has to have in order to avoid distortion in the output?yup, i have learnt derivative. With your comment of "the maximum slope is just the steepness at the point where the steepness happens to be steeper than anyplace else.", I now know the meaning of max slope. The signal changes the most per unit time at the point where the value of y at the y-axis is zero [only true is the sine wave starts at the origin (0,0)] What would happen if the amplifier generating that signal was incapable of changing as fast as the sine wave does at that point? I would say slew rate occurs. Its like the signal will try to get shortcuts to comply with the changes, which is why some rise time and fall time of the slew rate is a straight line and distortion will occur.
Its 2 pi F V right?So if I have a signal that is a pure sine wave at a frequency f and with an amplitude A and I pass it through an amplifier with a gain of K, what is the minimum slew rate that my amplifier has to have in order to avoid distortion in the output?
Hi,Alright, here is what I know. The slope of a ramp has distortion with a flat peak (just like the slew rate waveform we see). The maximum slope of a sine wave is round, meaning the curve goes up and reaches the max point and then it goes down, or it can be the other way round.
Did I get the facts right? If no, may I know where did I go wrong? And what should I look for next?
Thanks
What is V?Its 2 pi F V right?
My understanding is that the slew rate refers to the output voltage and is not significantly affected by the gain or the input voltage (except as how they pertain to the output voltage).Are you saying that the amplitude of the input signal and the gain of the amplifier play no part?
Hi,What is V?
Are you saying that the amplitude of the input signal and the gain of the amplifier play no part?
Does this give a hint as to where I might have been going?Hi,
I'd like to see where you are going with this
[EDIT] I see cruts also commented
Offered Answer:So if I have a signal that is a pure sine wave at a frequency f and with an amplitude A and I pass it through an amplifier with a gain of K, what is the minimum slew rate that my amplifier has to have in order to avoid distortion in the output?
My response:Its 2 pi F V right?
Let me be more specific since apparently I wasn't sufficiently clear. The question asked what the minimum slew rate of an amplifier with a certain gain needs to be in order to avoid distorting the output given an input signal that is a pure sine wave with a certain frequency and a certain amplitude.What is V?
Are you saying that the amplitude of the input signal and the gain of the amplifier play no part?
I never claimed that an amplifier's slew rate is affected by the gain or the input voltage, but I most definitely was implying that the minimum slew rate that an amplifier needs to have IS impacted by the gain and the input signal and that, therefore, an answer to that question that does not involve them is most likely not correct.My understanding is that the slew rate refers to the output voltage and is not significantly affected by the gain or the input voltage (except as how they pertain to the output voltage).
Of course it matters, to the extent that it affects the output voltage and required slew rate at the output.leave it to you to explain why the nature of the input signal and the gain of the amplifier don't matter when determining what an amplifier's minimum slew rate needs to be.