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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Need help analyzing sability of op-amp in a current source in LTSpice

I have to perform stability analysis on an op-amp (AD8671) which is being used as an op-amp in the circuit attached. I am using LTSpice to perform this. My approach is to give a 1V AC small signal at ...
496 views

How can these passive RLC circuits change a sinusoid's frequency?

Given a sinusoid input of frequency f, an RLC network, no matter how complex, should produce a sinusoidal output of frequency f, with possible attenuation and phase shift. At least that's my ...
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70 views

Frequency response open circuit time constant having trouble finding the resistance of a certain capacitor

*The problem (Fig.1) (From Microelectronic Circuits SEDRA/SMITH 7e Fig. 10.40 (b)) I'm finding the 3 dB frequency of this circuit using the open circuit time constant, and I met a problem while ...
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56 views

Why is Cgd4 part of CL? Smith Microelectronics Differential Amplifier Frequency Response [closed]

Figure 10.37 is the small signal analysis of Gm of the differential amplifier. The analysis combines all the capacitors in the MOSFETs into Cm and CL. I'm asking for the formula of CL. The textbook ...
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89 views

Gain bandwidth calculation of two stage op-amp

I want to design a two stage single ended OTA without using a Miller compensation capacitance. Every source that I have examined gives a design example with a compensation capacitance. Hence, they ...
329 views

What does Gain mean when LTSpice plots Gain vs Frequency in AC analysis?

I am trying to simulate the frequency response of a trans-impedance amplifier in LTspice, with a current source input, as shown below: My question is when doing ac analysis, the gain that LTspice ...
289 views

Order of an RC circuit and independent initial conditions

I am trying to determine the order of the transfer function of the RC circuit shown below. I learned that the order of the transfer function is equal to the number of independent initial conditions ...
• 115
70 views

Why is the actual circuit bandwidth so low for this TIA?

So, I roughly implemented the TIA, I found in this paper using a transistor array CD-4007's PMOS-es and a single discrete 2N7000 NMOS transistor. I also use a 1 Mega Ohm resistor to measure my output ...
178 views

Confusion about finding poles by inspection

I have a few doubts regarding finding poles by inspection and why sometimes the 'quick, intuitive' techniques do not work. Question 1 Consider the circuit shown in figure 1 below: By manually writing ...
• 3,145
154 views

How do I design a Multistage Amplifier with given specifications?

I have been tasked to design a multistage amplifier with the following specifications: Gain(V/V) = 30, Rin = 20 kohms, Rout < 25 ohms, Power supply = Dual +12V -12V, Max Symmetrical Swing > 9Vpp ...
1k views

Why is a peak in the gain a sign of instability in a closed loop op-amp circuit?

I watched a tutorial video that mentioned that when there is a peak in gain (dB), it is a sign of instability in the op-amp circuit. Is this statement always correct? If yes, can any one please ...
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1 vote
47 views

How to read graphs for a simulated EMI filter

Hello everyone, I'm in the process of designing an EMI filter for a charger that is meant to connect to a trucks 12 V output. I've based the design of the filter off of the MAX17703 evaluation kit (...
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77 views

In LTspice, is there any way I can obtain the frequency response of power converter alone?

I am aware of the following methods. But my intention is to understand the behavior of power converter alone, before adding the controller and feedback loop. FRA analysis: Provides the open loop ...
• 3,032
66 views

3-pole LC filter design

When designing a 3-pole LC filter with a ferrite bead as inductor L, using capacitor values intended for a LC filter with an inductor (not a ferrite) produces a large 'dip' or 'bounce' in its ...
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64 views

LTspice Bode plot filter analysis

I am designing a π-type LC filter with a frequency cutoff of approximately 1khz. Simulating the filter in LTspice gives the following Bode plot. It starts dropping off at ~100hz before dropping ...
• 592
129 views

Clarification of the loop response of a TPS54350 buck converter (LTspice)

I've modeled the equivalent model for the TPS54350 shown on page 14, Figure 23, using component values from application circuit on page 15, Figure 24. I'm feeling quite rusty on my controls knowledge ...
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107 views

Stability issue: Compensation changes using Bode plot in LTspice

I am encountering issues with a LT8390 design, particularly in higher load current conditions, which leads me to suspect a stability problem. The design parameters are as follows: vin 18-36 (28v ...
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83 views

Theoretically, if we send a square wave, of frequency equal to the pole frequency, through an RC lowpass filter is the output shifted by -45 degrees?

The square wave power is concentrated at the pole frequency with harmonics at integer multiples of this, so this main component would be phase shifted by -45 degrees and attenuated at .707*Vin and the ...
55 views

Transfer functions to determine voltage of a similar circuit

Goal is to solve for the voltage u2(t) I'm somewhat confused by this. I solved the transfer function Z(s) earlier in the top circuit, which is simply just Z. The voltage across Z in the top circuit is ...
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120 views

Why do these two NMOS frequency responses give significant differences in LTspice simulation?

The first is the schematics from NMOS4 with parasitic capacitance: From DC analysis: --- MOSFET Transistors --- Name: m3 Model: nmos-sh Id: 2.21e-04 Vgs: ...
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536 views

Multiple resonance frequencies of common-mode choke

In the datasheet of the CMC (common-mode choke) below (Würth Elektronik 744830017132), the impendence vs frequency graph has multiple peaks (resonances) which I marked. The first one is the Self ...
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120 views

MP28167-A DC-DC converter recommends a resistor T-network in feedback loop

I am designing a DC-DC buck-boost converter using the MP28167-A, and the datasheet contains this section: I understand the need for a resistor divider such that the closed-loop control regulates the ...
57 views

Help demonstrating mathematically the behaviour of a passive filter

Consider the following circuit: By inspection, it can be said that the complex impedance of the circuit will be $R_2$ for very low frequencies and $R_1$ for very high ones, as the inductor will ...
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67 views

My Sallen Key Butterworth high pass filter's frequency response graph is not responding

I tried to make a cutoff frequency of interface in partial discharge but the response frequency graph is not responding. I already changed (Amplitude= & frequency= 50Hz) in the sine generator ...
47 views

Bad AC response from bridge circuit

Followup to this question. Hi. I have the following bridge circuit to simulate a strain gauge. I am conducting an AC sweep of it as another part of my circuit (currently disconnected) that uses the ...
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1 vote
121 views

Inverting opamp amplifier: frequency response not compatible with LTspice simulation

I have a simple inverting opamp amplifier and I want to study the frequency response of the circuit and finally calculate the frequency band (or cutoff frequency). Unfortunately the model created in ...
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56 views

Breville 800ESXL [closed]

This coffee machine is specified as using 110 or 220 volts but always at 60Hz. Will it work at 50Hz? I cannot see any issue except for the pressure pump not reaching its maximum speed.
225 views

Find resistors for an inverting op amp band pass filter

I'm trying to save a problem that shows the following band pass filter: Note: the op amp doesn't need to be a TL081, it's an abstract, ideal op amp. I need to find resistors $R1$ and $R2$ so that ...
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158 views

Converting dBV to dBSPL

I am calibrating my microphone system consisting of a microphine whose signal is amplified and then converted from analog to digital with an ADC. The ADC converts the data to a 16-bit integer. The ...
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1 vote
113 views

Bandpass Amplifier

This is my frequency response , the point is if i change the capacitor values C1 and C4 my signal distorts on the second lobe in time domain and gain curve is not flat in the range. MY bandwidth is in ...
110 views

Measuring flyback SMPS feedback loop response

I'm trying to measure the feedback loop on a isolated flyback SMPS. My goal is to determine the phase margin and 0 dB cross-over frequency. The most common circuit I have seen is the one recommended ...
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195 views

Why is the frequency response from my 1X and 10X probe seem to be converging with increasing frequency?

I'm a Mechanical Engineer trying to get into electronics so please excuse my lack of understanding. I'm feeding a 5.0 Vpp sine wave into my SDS 1202X-E scope from my signal generator (see image below)....
256 views

How to measure the frequency of a low frequency signal?

I am looking to measure the rpm of a wind turbine, the wind turbine is 3-phase synchronous generator, the frequency range I am looking to detect is between 1Hz to 60Hz, I tried to use a frequency ...
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1 vote
272 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 ...
135 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 ...
38 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 ...
100 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. ...
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1 vote
46 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
70 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: ...
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1 vote
96 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 ...
96 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
290 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 ...
207 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 ...
62 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 ...
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37 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 ...
• 3,032
148 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 ...
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114 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 ...
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186 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 ...
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418 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?
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1 vote