37
votes
Accepted
What does a Bode plot represent and what is a pole and zero of a Bode plot?
Bode plot
Take a typical 2nd order low pass filter amplitude response bode plot: -
3-D picture introducing pole-zero diagram
Here's the bigger picture of that response when combined with a pole ...
- 388k
11
votes
Accepted
Why is frequency not measured in db in bode's plot?
Frequency is not a measure of signal amplitude or power hence, talking about "this or that" frequency in decibels makes no sense. If somebody says "increase the frequency by 3 dB"; ...
- 388k
11
votes
Why is frequency not measured in db in bode's plot?
We could start using dBHz and see how it feels. My guess is it won't make life any simpler or help understanding.
NOTE however : logarithmic frequency scale is already in use, and has been for a while ...
- 66.1k
10
votes
Accepted
Exciting an RC Circuit at its TRUE Pole on the Sigma (Real) Axis in the Left-Half Plane
Good question, here's my attempt. You still have to convert your input signal from the time domain to s domain, then do the math, then convert the result back to the time domain. That pole just tells ...
- 1,881
8
votes
Accepted
Identify zeroes of circuit by inspection
Inspecting a circuit to determine if there are zeroes is part of the fast analytical circuits techniques or FACTs as described in my book on the subject.
The first thing is to place each energy-...
- 15.1k
7
votes
Accepted
Intuitive to get pole and zero points for lead compensator
Yes, there is an intuitive approach and it with the fast analytical techniques (FACTs). Reduce the excitation to 0 V (\$V_1=0\$ and look at the resistance driving the capacitor (you temporarily remove ...
- 15.1k
7
votes
Low Pass Filter Wrong Pole Location
It's just a conversion from radians to degrees. The expression for a capacitor's impedance uses units of radians/sec. for frequency. The simulator is reporting frequencies in Hertz. 10 rad/sec is 1....
- 2,530
7
votes
Switching frequency and controller's crossover frequency in DC-DC converters
Crossover frequency selection is a bit more complex than to simply say "1/5th or 1/10th of the switching frequency" for the loop 0-dB crossover point. For a buck converter operated in ...
- 15.1k
6
votes
What exactly is Pole Frequency in a Filter and how does it affect the frequency response?
1) Why does the magnitude Bode Plot of the response of a filter NOT
approach Infinity at a pole?
Try looking at this picture and recognize that poles may exist as infinities in the bode plot but ...
- 388k
5
votes
Meaning of zeros in transfer function
1)zeros with positive real part give a negative phase contribution, reducing the phase margin (which is bad) thus limits the performance of the system.
2)Time delay in the system can also be ...
- 213
5
votes
Meaning of zeros in transfer function
There are zeros that can be located in the same region as unstable poles (that is in the right-half \$s\$-plane or outside the unit circle in the \$z\$-plane). But when zeros are out there, it doesn't ...
- 1,571
5
votes
Accepted
Low Pass Filter Wrong Pole Location
Complex Number Diversion
Complex numbers have both a Cartesian notation as well as two equivalent polar notations. The Cartesian notation, \$a+b\:i\$, is very hard to use in electronics but it is very ...
- 70.8k
5
votes
Zeros and poles in the following bode plot
How is it possible to make transfer function to become zero or
infinity.
You will only get zeros and poles in the bode plot if those zeros and poles lie on the \$j\omega\$ axis. The bode plot is ...
- 388k
5
votes
Why is frequency not measured in db in bode's plot?
While drawing bode's graph paper where Y axis is gain given in db while the X axis is frequency given in absolute value but scale used is log.
So we are plotting log response against log frequency.
...
- 143k
5
votes
Why is a capacitor to ground a low frequency pole, instead of a high frequency zero?
I intuitively expect the capacitor to cause a zero for those high
frequencies, not a pole.
It does create a zero but only when the frequency is infinite.
For more normal frequencies (such as the 3 dB ...
- 388k
4
votes
Finding Transfer Function, Poles, Zeros of an RC Circuit
Using impedances (forgive the lack of standard forms along the way) and going long-hand from scratch, I get:
$$\begin{align*}
\frac{V_O}{V_I}&= \frac{R\:\vert\vert\: C_2}{C_1+R\:\vert\vert\: C_2}\...
- 70.8k
4
votes
poles and zeroes, why the magnitude plot contradicts the actual definition
What is the intuitive way to understand this ?
There is a certain amount of intuition but there's more math than intuition I would say. Below is an example I use a lot: -
The top 3 pictures show the ...
- 388k
4
votes
What exactly is Pole Frequency in a Filter and how does it affect the frequency response?
All depends on the variable you're using to represent your transfer function (TF). The definition of pole you know is based on using the complex variable s. Indeed, in that case you have that poles ...
- 163
4
votes
Why is frequency not measured in db in bode's plot?
Gain is relative, frequency is absolute. A dB with no reference can refer to a gain because a dB with no reference is relative. Absolute levels require a reference value to have units in dB, examples ...
- 502
4
votes
Exciting an RC Circuit at its TRUE Pole on the Sigma (Real) Axis in the Left-Half Plane
KD9PDP's answer alreay explains very nice (+1) why the result is as you see it, but there might be an easier way to do it. You already have the impulse response (1) and the input (2):
$$\begin{align}
...
- 18.3k
3
votes
Accepted
RHP zero with a positive phase shift
The correct way to write a transfer function featuring a single zero is \$H_1(s)=1+\frac{s}{\omega_z}\$ and a single pole is \$H_2(s)=\frac{1}{1+\frac{s}{\omega_p}}\$. The plus sign implies that when \...
- 15.1k
3
votes
The Pole Frequency of OP AMP 741
1) The 741 is ancient, even though your work might be purely theoretical I suggest forgetting about the 741 and to choose a more modern opamp, also read Reasons no use a 741 Op-amp. I'd choose an ...
- 79k
3
votes
Accepted
What is the difference between the forward transfer function and closed-loop transfer function?
I just wanted to make things a bit more clear here because it seems that the idea of open loop/closed loop/forward transfer function has got a bit mystified and does not seem exact even though it ...
- 321
3
votes
Conjugate, non-conjugate and single poles in an RLC circuit system
The circuit you have drawn, the \$RLC\$ network, does not feature zeros, only poles. Should you add a small resistance in series with the capacitor, then you would add a zero. The equation you have ...
- 15.1k
3
votes
Accepted
What happens to an electrical system at its pole?
This picture might help: -
Along the top of the picture there are three bode plot examples of the magnitude response for a 2nd order low pass filter. These are just examples that show how the damping ...
- 388k
3
votes
Find the Zero of a simple circuit
Well, finding the zero by inspection requires some mathematical abstraction. When you perform harmonic analysis, you only consider the vertical axis and \$s=j \omega\$. When you inspect a circuit, you ...
- 15.1k
3
votes
Zeroes of transfer function
Consider a simpler one-rung ladder with just L2/C4 and C3/L1/R3.
Let the impedance of L2/C4 be:
$$\small Z_1=\frac{a+bs}{c+ds}$$ and the impedance of C3/L1/R3: $$\small Z_2=\frac{e+fs}{g+hs}$$ where \$...
- 7,323
3
votes
Accepted
Do we analyze real poles the same way you analyze complex conjugate poles?
I would recommend to factor the original formula in a low-entropy form and match the normalized polynomial of a second-order system which is: \$H(s)=\frac{a_0}{b_0}\frac{1+a_1s+a_2s^2}{1+b_1s+b_2s^2}\$...
- 15.1k
3
votes
Exciting an RC Circuit at its TRUE Pole on the Sigma (Real) Axis in the Left-Half Plane
If the system's impulse response is \$h(t)=e^{-at}u(t)\$, \$a>0\$, where \$u(t)\$ is the unit step function, and if its input is \$x(t)=e^{-at}u(t)\$, then its response is given by
$$y(t)=te^{-at}u(...
- 3,613
3
votes
Why is a capacitor to ground a low frequency pole, instead of a high frequency zero?
You are probably mixing some meanings for the term "zero". Think of it like this: in a transfer function it represents the root in the numerator, so it "zeroes out" higher ...
- 18.3k
Only top scored, non community-wiki answers of a minimum length are eligible