# Questions tagged [step-response]

For questions about the step response of an electrical system, which is the response of the system in the time domain to a unit step function input. Important characteristics of the step response include rise/fall time, overshoot, ringing, and settling time. Consider using in conjunction with related tags such as "rise-time", "control-theory", etc., if applicable.

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### How can current still exists as t approaches infinity in RL circuit

The textbook solution for $b)\ (\ i_{o}(t),t\geq 0\ )$ is $$\ 1.25e^{-1500t}-1.25A,$$ but as $t$ approaches infinity, the current will be $-1.25A$ for $i_{o}$. How can this be possible, ...
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### RL parallel circuit

This problem is available on MIT coursware assignements 9. Knowing that I(t)=4-10u(t) mA; R=1 kOhm; L=1 mH I want to find: a)IL(t=3.00E-06 s) b)V( t=3.57E-07 s) c)IR(t=1.90E-06 s) V is the voltage at ...
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### In a bandpass filter, when a square wave is applied into the input, why is the output a sine wave?

So I have designed a second order resonant bandpass filter with a center frequency of 320 Hz and a peak gain of 10. It works perfectly fine, however, I am just wondering why when the input is a square ...
186 views

### Why is step response of an opamp linear/exponential?

My step response for LM741 at LTSpice was this: And for TL081: So as you can see the response of LM741 is linear and of TL081 is exponential, but why? My schematic is an inverting amplifier with v=...
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### NE555 pulse extender for PIN photodiode radiation detector is it fast enough? And more

I've designed a circuit using a PIN photodiode for a radiation detector aimed at identifying radium in an old watch. However, I'm uncertain about its effectiveness, particularly regarding the speed of ...
90 views

### Damping gets better, but overshoot increases. How can I explain it?

I have three transfer functions as below The pole-zero plot and the step response of the transfer functions are given as It makes sense to me that G3 has a better damping than G2 and G2 has a better ...
47 views

### How does this work? Finding final voltage of capacitor in a RC circuit step response problem

There is a circuit with a switch which was in position 1 for a long time and is now in position 2. I attached a picture of the given circuit below. Once in position 2 I need to find the final voltage ...
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### Why can I ignore this part of the circuit during step response analysis?

I'm doing a RL step response analysis problem and I am confused on why we are able to only consider the left side of the circuit when the switch moves from position a to position b. "The switch ...
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1 vote
55 views

### Help for RL step response

Here is the question I am trying to solve: I didn't find Vo(t). What way should I go to find this value? ( Vo(t) is a voltage on 40k resistance after switch moves b.) Here is my attempt: ( It looks ...
246 views

### Need help to find step response of RL circuits

Here is the question I am trying to solve: I drew my solution with calculations on paper. Before the key is closed, I calculated İ0 and then after the key is closed, I calculated the last current (I∞)...
110 views

### Derivative of a waveform

I am self studying linear circuits and I came to a very basic problem. The problem: $$y(t) = e^{-t} u(t)$$ where $u(t)$ is the step function. Calculate the derivative of $y(t)^{\prime}$. My take ...
247 views

### Unexpected output from LC circuit

I am trying to get back into some electrical engineering basics, and had a quick question regarding an unexpected output I am seeing. I am trying to learn about RLC circuits again, and wanted to build ...
1 vote
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### What is the correct way of replacing the value of a step voltage source in Laplace?

I'll be presenting two ways to reach the same answer. I would like to hear which way is the correct way to get there. I am not interested in the result, it's the same in both cases, I'm interested in ...
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### How to implement PWL or step function in CircuitLab?

I tried to implement a simple PWL (Piece Wise Linear) function in CircuitLab, and it does not seem to work. It differs slightly from LTspice, which I know how to use. The data points are in CSV (Comma ...
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### How to prove property of transfer function for causal LTI system

For causal linear time-invariant systems the degree of denominator must be larger or equal than the degree of the numerator. How can this be proven rigorously?
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### How to derive phase margin and gain margin from experimental step response?

I have a fabricated closed-loop integrated amplifier circuit. Therefore, I can only conduct transient response experiments. How Do I derive the phase margin and gain margin from the experimental step ...
345 views

### Step response of critically damped PID controlled system

I thought that by definition: critically damped 2nd order system (ζ=1) does not have overshoot. Is the above assumption wrong? It might be on the verge of oscillation, but, it shouldn't oscillate. ...
201 views

### How to sketch the waveform of the voltage across capacitor and find equation that describes it? [closed]

Below DC voltage source, a switch, resistor and capacitor. At time $t=0$, $C$ has zero voltage across it and switch is closed. How do I sketch waveform of voltage across capacitor v/s time and ...
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### Differential equation of a LC circuit in series with a parallel RLC circuit

I have the following RLC circuit. I am having trouble finding an expression for the natural response of this circuit. I found a similar question, but I was unable to simplify exactly like was done in ...
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### How to calculate natural frequency and zeta of underdamped, 2nd order system if only given experimental data?

How do I estimate the values of $K$, $\zeta$ and natural frequency, given the plot of unit step response of the system in time domain? I figured that at $t = \infty$, $Y(t) = K$ and I ...
194 views

### Graetz diode bridge with series LC circuit oscillation problem

I am trying to understand a problem I have encountered. I simulated the voltages on a Graetz diode bridge with a step voltage input of 24 volts. The schematic and the voltage signals are given below. ...
906 views

### High pass filter: Overshooting before attenuation

Working with a 2nd order Sallen-Key high pass Butterworth filter with a cutoff frequency of $f_c=0.5$ Hz I am having difficulties making sense of a result that I got: After applying at its input a ...
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### Harmonic response of PID only works if multiplied by a large number?

I am trying to control just one motor using a H-bridge as shown in the picture (one motor only). I am attempting to use PD control, but for some reason I only obtain a sin wave when I multiply sin(x) ...
149 views

### Using lag-compensator to get good system response - RHP zero

I am designing a velocity controller for a balancing robot. The most important thing for the robot is to maintain balance, so I would prefer a slower response velocity response in turn for a steady ...
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### Velocity control system is stable even though CLTF has a pole at s=0?

I was reading about steady error calculation for system with H(s) having Nth order Zero at s=0. In book it is written that steady error calculation is meaningless when closed loop transfer function(...
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### Finding the output time response of a transfer function with a step response

The question is finding the output time response of the transfer function below. I solved that it is an underdamped response. The step response is 1/s. $$T(s)=\frac{20}{s^{2}+6s+144}$$ According to ...
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### Can I remove my step response overshoot?

I am working on a balance controller for a robot. I found the open loop transfer function between the motor voltage and robot pitch angle: ...
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1 vote
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### RC filter impulse response is exponential decaying but inverse Fourier is Sinc function

As we all know that the inverse Fourier transform of a frequency domain unit pulse/rectangular function (which looks like low pass filter) is Sinc function. So, I was under the impression that any low ...
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### How can I find the current in the resistor,when I found inductor current in this question?

Previous part of the question, I found the inductor current (from natural and step force). But here, I think it asks 10 ohm resistor's current. How can I find it ?
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### What happens when the direction of initial current through an inductor is opposite of the direction of applied current?

I am having trouble understanding the behavior of current through an inductor when the direction of applied current is the opposite of what is initially flowing through it. An example is that when an ...
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### After being open for long time, the switch in circuit closes at $t=0$. Determine $I_1(t)$ for $t>0$, Steady State Current and Initial Current

I am seeking guidance on this Assignment [Homework] Problem regarding RL circuits because me and my study group are getting two different answers and we don't know why. Question : After being open ...
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### Is there an English word for the output response of a non-minimum phase system?

I've noticed in some French language control courses they have a word for the initial part of the response of a non-minimum phase system. They say it has "un départ malin". I looked up ...
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### Confusion Between Dual Capacitor/Inductor Circuits

I'm trying to physically understand the responses of this pair of (dual) circuits: a step current source driving a capacitor and a step voltage source driving an inductor. simulate this circuit &...
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