# Questions tagged [frequency-response]

For questions about the frequency response of electrical circuits. Also consider using the related "bode-plot" and/or "nyquist-plot" tag if your question involves a Bode and/or Nyquist plot, and/or the "stability" tag if your question is about the stability of an electrical circuit.

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59 views

### Difference between tone control circuits in a simple op amp overdrive pedal

I am trying to understand the differences in operation and frequency response of the following tone control circuits. This question only applies to the sections circled in red. The rest of the ...
45 views

### Why does MATLAB show a pole in bode plot of an underdamped second order system at natural frequency?

I am using the sisotool in MATLAB to obtain the bode plot of the following transfer function: MATLAB marks a pole at wo which is approximately 11.18 What is the meaning of this? How would you even ...
37 views

### How can I explain contradictory damping performance between linear and nonlinear systems?

I have a 3rd order nonlinear dynamical system, representing a power system. After linearizing the system, it turns out that by increasing the parameter L_g, damping is reduced and thus the overshoot ...
49 views

### Simulating frequency response of switched capacitor circuit

A web search of "simulate switched capacitor circuit" gives several results which suggest the use of periodic AC analysis to find the frequency response of a switched capacitor circuit. ...
1 vote
35 views

### How to provide a low response time <1µs constant current source up to 1.5A

I need to provide a constant current source that can provide up to 1.5A current and a compliant voltage of 0-40V, with a low response time of <1µs. How should I approach this problem? Common bench ...
1 vote
60 views

### Problem with analog passive lowpass filter

I designed a lC low pass filter and instead of getting a frequency response of lowpass, I got a strange frequency response as mentioned in the figure below. Does anyone have an idea ? The circuit: ...
1 vote
54 views

### Help with defining an induced voltage in LTspice and setting frequency dependent parameters

I am trying to set up a similar circuit in LTspice and making necessary modifications to change it to a bandpass filter. I have a couple of questions regarding this model and was hoping someone could ...
63 views

### Calculating frequency response of a RF tuned collector amplifier

I am doing a frequency response analysis for the following RF tuned circuit. I am not sure if I have done the right calculations so please correct me if there is any mistake. The DC equivalent ...
1 vote
207 views

### RF Circuit shows flat frequency response for BJT amplifier in LTSpice

I am analyzing a signal jammer circuit for prototyping on LTSpice. The amplifier takes a square wave signal input from NE555 IC and is supposed to transmit it at ~2.4GHz using a tank circuit at ...
90 views

### Basic RF signal amplifier

I made an 8 Mhz shortened antenna with a length of 12.3cm and wire diameter of 2mm by a 220uH bobin at the bottom. The transmitter and the receiver circuits have the same antenna configurations. The ...
40 views

### Is there a correlation between conditionally stable systems and non-minimum phase systems?

I know bode plots cannot be used for non-minimum phase systems ( eg: delay, Boost converters). Can we identify the closed loop conditional stability from open-loop bode plot response? Conditional ...
25 views

### Is it correct to use the concept of phase margin for not so 'well-behaved systems'?

The TI document mentions the Phase margin as 60 degree for the given bode plot whereas the lowest PM when Gain >1 is around 45 degree. Wiki says: " Ordinarily, as frequency increases the ...
54 views

### Frequency response measurement of power converter - Why is the injection point across the resistor?

The standard procedure of measuring the frequency response of a buck converter is to inject a small voltage across a small resistor Rt as shown below. (Ref @4:40) Why do we apply the input voltage ...
101 views

### frequency-dependent network equivalent in time domain simulations

I have this question that has been haunting me for a while now. We all know that the first solution we think of when willing to account for frequency-dependent behavior in time-domain simulations, is ...
31 views

### Frequency response of a series RL circuit

I connected the larger coil of this ferrite rod aerial (which according to it's datasheet, should have an inductance of 200 uH) in series with a 10 ohm resistor and just left the smaller coil open. ...
1 vote
104 views

### Power converter: Why we always focus on loop gain involving control to output transfer function?

While measuring loop gain using AP300 frequency analyzer, why we always focus on loop gain involving control to output transfer function? Is it because input to output transfer depends on power stage ...
353 views

### Frequency analyzer for loop gain measurement - Why should the injection point have low output impedance and high input impedance?

@5:08 The video mentions: "The insertion point should have a low output impedance and high input impedance" What is the background for this condition?
1 vote
42 views

### Is there any significance of RHP zeroes on a system's open loop behavior?

In a closed loop boost converter, RHP zeroes will cause a phenomenon called ‘non-minimum phase’, which will make the closed loop system go in the opposite direction first when an external excitation ...
360 views

### Finding frequency response of inductive EMI sensor

I'm building an EMI sensor and trying to understand how it's done with the Elektrosluch. Here's the full schematic but this is the part I'm concerned about: simulate this circuit – Schematic ...
1 vote
92 views

### Can a frequency multiplier (e.g. doubler) impact signal bandwidth?

My understanding is that if a single tone at frequency F is input to the frequency doubler, one should observe at its output in the spectrum the same tone but now at a frequency 2F. What happens if ...
1 vote
60 views

### Finding an analytical expression for a current distribution for conductors in parallel

Recently, I tried to set up an experiment at home to study what path the current takes at different frequencies for the circuit below. I think this will be a fun project, but I'll need your help. I ...
1 vote
273 views

### Frequency response of coupled LC oscillators

We can use coupled LC circuit to understand the normal modes of coupled oscillators of a lattice. We are using this to get the dispersion relation of the angular frequency for the oscillation. ...
26 views

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### Control loop simulation of a LM5117 buck converter, CM mode, using LTspice

I am trying to perform a control loop simulation of a buck converter based on a LM5117 chip. It will be used for battery charging, hence the output voltage and output current should be regulated. The ...
164 views

### Elliptic filter - implementation deviates from the design and simulation

I have designed a 7th-order elliptic filter using this online tool. Cut off frequency - 15 MHz Pass band ripple - 0.1 dB Stop band attenuation - 70 dB I've asked it to use tge standard inductor value ...
1 vote
85 views

### Why isn't the frequency response of this filter the same in these two circuits?

Below is the filter with ideal op amps and its frequency response: Below is the filter with real op amps and its frequency response: Very different responses from both circuits... The frequency ...
43 views

### Would a square waveform (or trapezoidal waveform) have frequency content lower than its fundamental frequency?

I was trying to understand the LC circuit response for the circuit given below. (Note: fsw indicates the frequency of input square wave as in a buck converter) As far as I know, for a linear circuit, ...
1k views

### Why is the frequency response of an LED important?

I'm working on visible light communication where I fabricate my own organic LEDs. One of the ways to characterize them is "small signal analysis." I understand we are applying this analysis ...
100 views

### Why does the Bode plot in LTspice disagree with my command calculation?

I am trying to use LTspice to plot Bode plot for frequency response. I used command to get the gain at the 1kHz first. In the error log it turns out that it is 47.3dB. When I used small signal AC to ...
1k views

### Why are there ripples in the passband of some filters, like the Chebyshev filter?

Please see the Bode magnitude plot as we steadily increase the input frequency to the filter. Why does the magnitude oscillate? What physical component(s) in the filter circuit is producing that ...
55 views

### Changing the frequency response of an open loop circuit op amp

Usually on the frequency response of an open loop op amp, the gain decrease greatly in the higher frequencies. How can we increase the gain from 50 hz to 25 khz to remain high at, say, 120 dB? The ...
67 views

### Factorize generic transfer function

This is not homework. I'm just trying to understand concepts and methods, and for that I'm using a generic Transfer Function for an Active Filter like $\mathcal{H}(s) = \frac{1}{1+BAs + A^2s^2}$. ...
1 vote
109 views

### Finding poles by inspection - 2 resistors

This is a follow on question from Finding poles by inspection - R to ground Is this correct? I have tried to follow the approach there.
1 vote
533 views

### How would a brushed DC motor react to high PWM frequency

After a lot of research and simulation tries, I cannot determine how a brushed DC motor would act if given a high PWM frequency, ignoring any losses in the controller due to switching. What I know so ...
455 views

### Is the cut-off frequency of a 4th-order filter at -12 dB or -6 dB?

I designed a 4th-order active Linkwitz-Riley crossover filter by cascading two 2nd-order Linkwitz-Riley filters. Below are the simulation results. The red and purple waveforms are taken at the output ...
185 views

### How to solve this problem using transient time-domain analysis?

Find V0(t) in this circuit assuming zero initial conditions. I solved it (refer image above) using frequency-domain analysis using Laplace and found the answer, but I am not able to get the same ...
103 views

### Order of RC circuit

In the given RC circuit, there are 3 capacitors, out of which the voltages of 2 capacitors can be uniquely determined. This implies that it is a second-order circuit. But when I found the expression, ...
225 views

### Phasor calculation doubles frequency?

When working with phasors we have $$\bar{Z} = A\cos(\omega t + \phi) = Re(Ae^{j(\omega t + \phi)}) = Re(Ae^{j\phi}e^{j\omega t})$$ where $$\bar{P}_1 = Ae^{j\phi}$$ is the phasor. But when we multiply ...
1k views

### Audio frequency response over Bluetooth

Introduction : Using some binaural beat meditation, the vendor claims that their sound frequency goes down to 5 Hz to get better meditation quality. Even though the human ear can't hear 5Hz, the brain ...
474 views

### How is transformer output affected by frequency?

Vp x Ip = Is x Vs Vp x Ns = Vs x Np In ideal case, it seems, frequency is not in the consideration. How will it be with real case considering core and conductor losses?
82 views

### Transfer function of two frequency spectra

When you have two amplitude frequency spectra (fourier spectrum), in this case of a torque ripple, how do you define the transfer function (or the ratio) between both? How do you "divide" ...
253 views

### Does a resonant peak produce a distorted wave form?

Context I am re-enforcing my understanding of the frequency response. From 1, I understand that, In an audio system, [the frequency response] may be used to minimize audible distortion by designing ...