9
votes
Accepted
Trouble with filter using Laplace transfer function in LTSpice
Save some grief: set \$\omega=1\$
Just save yourself some algebra grief and set \$\omega=1\$ when focused on a particular filter shape (like Bessel.) The filter shape can be moved around freely (at ...
- 5,672
5
votes
Accepted
strange phase behavior RC low pass filter
Electrolytic capacitors have fairly large ESR values, and they're fairly constant across frequency. As the reactive impedance drops according to frequency, the total impedance becomes dominated by ...
4
votes
Trouble with filter using Laplace transfer function in LTSpice
I suppose that the mentioned frequency (f=3.5 kHz) is the desired 3dB-frequency (your requirement), right?
In this case, it is not true that the corresponding w value (2Pi*f) would appear in the ...
- 25.7k
3
votes
How to filter a noisy PWM signal without affecting rise and fall times
What filter would you recommended to clean this signal without affecting the rise and fall times
Mathematically, it's impossible to do this with a linear filter, as a sharp edge has an infinite ...
- 90.5k
2
votes
Accepted
Find resistors for an inverting op amp band pass filter
The input pair of components create a high pass filter, the feedback pair of components create a low-pass filter.
Using f(-3dB)=1/(2 * pi * R * C) for each pair of components (input pair and feedback ...
- 496
2
votes
Do I need to add a filter for an isolated DC-DC converter?
The test configuration is a circuit that is used to test the performance of the DC-DC converter under controlled conditions. It is not necessary to use the test configuration for normal operation of ...
- 29
2
votes
Trouble with filter using Laplace transfer function in LTSpice
The Bessel coefficients from Wikipedia yield a filter with unit group delay, not unit cutoff frequency. It is thus not surprising that you don't get the cutoff frequency you expect.
What is your ...
- 2,555
1
vote
Accepted
Why would a low-pass filter be connected to +5V on an RS422 differential line?
In a multi-node network, the RS422 drivers each have tri-state outputs that can go into a high-impedance state to allow other drivers to drive the bus. When all of the nodes are in this state, the ...
- 10.6k
1
vote
Find resistors for an inverting op amp band pass filter
Well, the transfer function of your circuit is given by:
$$\mathscr{H}\left(\text{s}\right):=\frac{\displaystyle\text{V}_\text{o}\left(\text{s}\right)}{\displaystyle\text{V}_\text{i}\left(\text{s}\...
- 7,378
1
vote
Discrepancy Between Bode Plot Predictions and FFT Output for Higher-Order Low Pass Filters on a 10 kHz Square Wave
Three of your plots have a 20dB/decade slope of the baseline, the three that went through your filter simulation. This baseline is obscuring what's happening to the harmonics, that will actually be ...
- 162k
1
vote
How to filter a noisy PWM signal without affecting rise and fall times
What filter would you recommended to clean this signal without affecting the rise and fall times of the PWM (such as a LPF would do)?
Do you simply need to measure the frequency and duty ratio of the ...
- 20.7k
1
vote
How to filter a noisy PWM signal without affecting rise and fall times
You should be able to filter out the high frequency component fairly easily, since it's an order of magnitude higher than your signal of interest.
Your signal is 88Hz, maybe up a couple hundred if you ...
- 6,613
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