# Tag Info

Accepted

### Stability of input filter in SMPS - Theoretical explanation

It is an extremely complicated subject. I have taught an APEC seminar in 2017 and tried to explain the interaction between a filter and a switching converter. First, you need to understand that a ...
• 21.1k
Accepted

### Meaning of Sigma in Laplace transform

As most folk know, $s=\sigma+j\omega$ (where $j\omega$ is the frequency along the x-axis in a bode plot or spectrum analysis). However, in a bode plot, $\sigma$ has no apparent meaning but it is ...
• 444k

### Under what conditions does jw equal the laplace variable s in an electrical circuit?

The Laplace variable $s$ relates to Fourier's $j\omega$ as follows: $$s = \sigma + j\omega$$ Fourier transform can be seen as a Laplace transform when $\sigma=0$. The $\sigma$ allows the ...
• 2,644
Accepted

### how the area is exactly zero?

The dirac-delta function has an area of 1 when integrated. The red area and the delta function have the same area. When integrated from t = (0-) to t -> inf the total area is 0.
• 2,081
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 ...
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• 4,800

### Transfer function of electrical network

A quick look at the fast analytical techniques or FACTs gives you the transfer function of this guy in the blink of an eye. First, turn the stimulus off or reduce $V_{in}$ to 0 V: replace the source ...
• 21.1k
Accepted

### Differential equation from a circuit: two methods give different results

The two results don't correspond because there are two different functions being used for $E$. In time-domain approach taken in the lecture, it is assumed that $E$ is constant for all $t$, ...
• 2,632
Accepted

### Euler's relation (e^(j*pi/4)

I don't know how you managed to get cos(pi/4) = 0.5 because cos(45) = 0.7071 and sin(45) = 0.7071 too. (These errors were subsequently edited out of the question). Hence $\sqrt{0.7071^2 + 0.7071^2}$...
• 444k
Accepted

### How to find the system response given the transfer function without using Laplace transforms?

I assume you are permitted to perform partial fractions, even if you aren't supposed to use $\mathscr{L}^{-1}$. The roots of your denominator are $p_1=-6+j\:8$ and $p_2=-6-j\:8$ and the root of ...
• 77.5k
Accepted

### Finding impulse response by a non-Laplace-transform method

Great question. Of course, transforms are the best way to solve this, which you already know. But maybe when you start with a bunch of numbers from an oscilloscope instead of a nice, neat formula, ...
• 2,632

### 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 ...
• 444k

### Confusions regarding Laplace transform

First, what is a transformation? A transform is a mapping of a function in one domain into another domain. To go from one domain to another, you need basis-functions (basis-vectors). In Fourier ...
• 3,891
Accepted

### Inverse Laplace transform

If you want to confirm your inverse transform with a specific circuit you need to come up with a particular solution. You can't just plug in a general solution. It seems as though you don't realize ...
• 77.5k

• 77.5k

### Laplace transform on simple low pass filter in Python

You're trying to plot in the time domain (ie. the x-axis is in seconds) but your formula is in the frequency domain (s is a complex frequency variable). You would ...
• 3,211

### How Fourier transform be able to deal with transients?

Check out any reference on Gibbs phenomenon. It essentially says that the Fourier series cannot fully accurately represent any repetitive signal with discontinuities. What one gets when the series is ...
Accepted

### Question about transient behaviour in op-amp circuit

Obviously, this cannot occur in a real circuit You have several problems. You are using derivatives on something that is discontinuous. That usually tends not to work. Also, the opamp's output ...
• 72.2k

### Does an impulse function at t=0 go to infinity, or 1?

The $\delta(t)$ is defined as positive infinite amplitude and infinitesimal width with an area of 1 at $\delta(0)$, and 0 otherwise. As Wikipedia states: \\$\int^\infty_{-\infty}\delta(t)~dt = 1\...
• 8,149
Accepted

### Why do we use Laplace transforms to analyse transient circuits?

It's easy to solve simple filter circuits in the time domain but there becomes a tipping-point where most engineers would prefer to solve problems in the frequency domain and apply (for example) a ...
• 444k