37 votes
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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 ...
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20 votes
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Why aren't active headphones equalized to a flat frequency response?

When you put something to your ear reproducing standard stereo recordings, you don't want a flat frequency response because the head-related transfer function that normally comes into play for a sound ...
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17 votes

Why is a capacitor considered a short circuit at start up?

You are mixing up two very different concepts. When you talk about impedance you are implicitly examining the behavior of the system in an AC steady state condition, i.e. when excited by a sinusoidal ...
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15 votes
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What is the difference between frequency response and transfer function?

A circuit's transfer function is a fully mathematical model that can be used to derive the frequency response and phase response (both together are called the bode plot). However the same isn't true ...
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13 votes
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Formula for Logarithmic (audio taper) pot

Although this question has been answered I just wanted to add something for those seeking an ideal logarithmic potentiometer law for simulation. A mapping from linear law to logarithmic law can be ...
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13 votes

Why does a square wave in frequency domain have less amplitude?

Any repeating waveform can be constructed from a series of sines of integer multiples of the fundamental frequency of the waveform. These are the harmonics. Using Fourier expansion with cycle ...
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9 votes
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Does a voice coil vibrate at the same frequency as the source sound file?

I would expect so, assuming the speaker is capable of vibrating with the same speed. As far as I know each speaker has a range in which it can vibrate (usefully). Mostly bigger speakers are better ...
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9 votes

Does a voice coil vibrate at the same frequency as the source sound file?

An ideal speaker will vibrate at whatever frequency of signal you drive it with. However, in reality, there are a few constrainsts. The amplifier output you are driving it with has a frequency range ...
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8 votes
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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-...
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8 votes

Intuitive understanding of relation between phase margin and peak overshoot and/or damping factor

There is a way to link the open-loop phase margin \$\phi_m\$ with the closed-loop quality factor \$Q_c\$. The exercise involves concentrating in the vicinity of the crossover frequency and ...
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7 votes
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Inductive reactance: frequency vs current. Why current goes to zero as frequency increases?

One way to look at this is that the inductor is a frequency-variable resistor (not quite since there's also a phase shift in there, but that's not important for this point). The higher the frequency, ...
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7 votes
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Frequency response of MCU decoupling capacitor

I agree with Lundin's comment that 1 uF is a bit of a high value, especially if you only use a 1uF capacitor. But to answer your actual question: yes, it will probably just work if your circuit's ...
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7 votes

Why are the theoretical and measured frequency responses off a low pass filter different?

What is the reasoning behind this other than measurement errors? tolerances of components wrong theoretical calculation incorrect measurement procedures (wrong impedance scope-probe) test equipment ...
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6 votes

Formula for Logarithmic (audio taper) pot

Usually audio taper pots are not logarithmic but a piecewise approximation with only 2 segments. Each segment of the track will be coated with different resistivity material or have a different width ...
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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 ...
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6 votes

Frequency response of dual vs single op amp: OPA2890 vs OPA890

Does this make any sense? Yes it does, from what I've seen they manufactures can use different silicon sometimes for a dual vs a single or quad part. But without actually seeing the die layout there ...
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6 votes

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 ...
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6 votes

Transmission Line Transient Response To Step Voltage Prior To Any Reflections

I am specifically asking whether the driving circuit will see the transmission line as a pure resistance according The Telegrapher's Equations, or whether those equations predict the driving circuit ...
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6 votes

Transmission Line Transient Response To Step Voltage Prior To Any Reflections

I am specifically asking whether the driving circuit will see the transmission line as a pure resistance according The Telegrapher's Equations, or whether those equations predict the driving circuit ...
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6 votes
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Why are low values of resistor in non-inverting configuration of opamp causing gain peaking?

It is due to the opamp's open-loop output impedance. As you can see in Figure 21 of the datasheet, the open-loop output impedance is inductive from about 100Hz to 10kHz. I modeled it using this ...
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6 votes
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Ideal closed-loop gain derivation for negative feedback

If you think more geometrically, then it's not terribly complex (sorry for the pun.) Multiplication of complex numbers is counter-clockwise rotation and scaling. Division is clockwise rotation and ...
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6 votes

LC Low pass filter in LTSpice

To expand on the other two answers, here is what you are plotting: 5MHz - 10MHz linear sweep. The height of the peak depends on the simulation resolution. If you change to a 10kHz-100MHz decade sweep,...
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6 votes

Why is a capacitor considered a short circuit at start up?

You are mixing up two different operating regimes for the capacitor. In the case where a constant AC sinusoidal waveform is put across a capacitor the impedance = 1/2.pi.f.C. In the case where a DC ...
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6 votes

Why is a capacitor considered a short circuit at start up?

This phenomenon can be better explained in time domain than in frequency domain. Strictly speaking, a capacitor is not a short connection since its terminals are separated by an insulator. It rather ...
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5 votes
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Is \$f_{\text{hfe}}\$ independent of BJT capacitances?

As you probably know, \$\beta\$ or \$H_{\text{fe}}\$ is in first order determined by the ratio of the doping of base and emitter. This doping ratio is intrinsic (determined during manufacturing), it ...
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5 votes

What is the difference between frequency response and transfer function?

The frequency response is a special case of the Laplace transfer function where the transients are assumed to be completely dissipated, leaving the steady state sinusoidal response. Take, as an ...
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5 votes
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Frequency response of dual vs single op amp: OPA2890 vs OPA890

It looks like there is an actual difference between the OPA890 and the OPA2890. For example, the parametric table on the OPA890's description page shows that the OPA890 has a slightly higher GBW (260 ...
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5 votes

High frequency response of capacitors

capacitor does not like the fact that voltage is changed across it since it acts as a short circuit initially I don't know what the capacitor likes or doesn't like, but I think your reasoning is ...
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5 votes

More equations than unkowns in amplifier circuit

Why going through a complicated analysis with KVL and KCL then ending stuck with a system of equations to solve? The fast analytical circuits techniques or FACTs are an interesting alternative to ...
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5 votes

More equations than unkowns in amplifier circuit

If you are familiar with the function could you please explain in an answer instead of simply saying that solutions might "exist somewhere on the internet"? Thank you! Not "might exist" but "do ...
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