# Questions tagged [passive-filter]

For questions about passive filters. Consider also using the "filter" tag, and use the "active-filter" tag if an active filter is part of the question.

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76 views

### Butterworth Filter for SMPS

If the performance of a Butterworth filter is dependent on the load impedance how do high voltage high power 1kW+ SMPSs manage to achieve smooth output ~100mV peak to peak across wide ranges of load ...
81 views

### Bessel Filter to separate AC and DC at Supply Level

I have a Supply Source composed of 150 VAC @ 400 Hz + 48 VDC. It is used to supply a big relay (~ 4 H, 1820 Ohm). I need to extract the 48 VDC, filtering out the 150 VAC. I designed the following 5th ...
99 views

### Help needed with RC Phase Shift Oscillator Analysis

I simulated the following circuit from page 439 of “The Art of Electronics, fig.7.23”. It works fine and outputs $\approx 1\ \rm{kHz}$ as expected. My question is around the theory, I expected the 3 ...
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72 views

### RC filter cutoff and impedance

I wanted to create RC lowpass filter with cutoff frequency 15 kHz and output impedance 50 ohm. What should be R and C values? I'm a little confused how to interpret 50 ohm output impedance to ...
64 views

### What happens if a low-pass filter and a high-pass filter are interchanged in a band-pass filter?

what happens in this circuit if I interchange the highpass filter and lowpass filter how does it affects the gain and phase shift
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1k views

### Why is my band pass filter giving a gain of 0.5 in the -3 dB gain region?

I designed a band pass circuit but it gives me a gain of 0.5 in the band region. Shouldn't it be 0.707?
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140 views

### How do I calculate how to change the cut off frequencies of this bandpass filter? [closed]

I am trying to find the transfer function of this filter to change the cut off frequencies later. When I do the calculations the traditional way the equation is very long and messy. Maybe there is ...
1 vote
82 views

### Is this the correct way to make a bandpass filter?

I'm trying to make a bandpass filter for a low voltage noisy electrical signal coming from a K-Type thermocouple To identify the frequencies I would need to filter out, I make a spectrum diagram using ...
1 vote
111 views

### Passive filter design from transfer function

I would like to implement a passive RIAA filter circuit. This is the bode plot of a RIAA equalizer. The transfer function of this: H(jw) = (jwT1 + 1)/[(jwT2 + 1)(jwT3 + 1)] where time constants are ...
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43 views

### How to determine band-pass frequency and bandwidth in photodiode TIA circuit

I'm trying to figure out how a photodiode amplifier circuit works. It is used in my university plasma physics lab to measure plasma density through laser interferometry. This circuit was designed 20 ...
1 vote
61 views

### How to determine the transfer function of this pi filter?

I have this pi filter, I wonder how do i determine the dynamic model and the transfer function of this filter?
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1 vote
39 views

### Derivation for capacitance and inductance formulas for Linkwitz Riley and Butterworth crossovers

I'm only a high school student but was looking into some aspects of crossover design. In particular, I was learning about this crossover: I understand the derivation of the crossover/cutoff frequency ...
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90 views

### Power over Coax (PoC) filter design calculations

I need to design a PoC filter for one of my project. I am referring this document for the same. Below is the PoC filter given in page in 13. I am using only TI parts. This document is from TI. This ...
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### Questions about eliminating oscillation and noise in a load cell system

I'd like to ask you for your expertise on a challenge I'm facing as part of an electronics project. A crucial part of this project is the integration of a force sensor, whose variation in resistance (...
71 views

### How do I run a frequency response analysis on a speaker cross-over circuit using Micro-Cap 12?

I've got a simple speaker cross-over network drawn in Micro-Cap 12, I'm using a resistor in series with an inductor to represent the speaker, I've got a sine source as a voltage source to the circuit. ...
1 vote
47 views

### Voltage divider with filter cap gain derivation

I am a mechanical engineer by training and I'm self-studying circuits. I'm trying to understand how to derive the gain and cut-off frequency for the following circuit: I think that I should use the ...
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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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### Simple Guitar Tone Adjustments [closed]

What passive-type tone adjustments are available to install on an electric guitar?
2k views

### DigiKey and others are incorrect about cutoff frequency for an LC filter

(At least I believe this is true.) If you Google "LC filter" and "cutoff frequency" you will probably see the formula 1/(2π sqrt(LC)). An example would be this online calculator at ...
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1 vote
95 views

### Transistor specs in the capacitance multiplier

I'm working on a constant current power supply and as a first step designed the following rectifier with a filter. I know the bottom rectifier is inactive, but with couple of switches the circuit ...
124 views

### SPICE (Spectre) "ideal" capacitive divider behavior

I decided to look at this after seeing this post, although I think they're not the same so making a separate question. I wanted to check what would happen in SPICE (this happens to be Spectre) if I ...
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146 views

### Maximum inductor current ripple in an inverter circuit

The following is the maximum current ripple of the system in the figure below: In the system in the figure below, how is the maximum current ripple for L1 derived? I know that diL/dt = DVL/(Lfsw) ...
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107 views

### In Bode plots what does phase tell us for passive filters (open loop)?

I was just playing around with a passive filter to erase some noise - one that should work between 80MHz and 1GHz. I'm aware that the phase in Bode plots gives data about the time delay between the ...
1 vote
192 views

### How do I go about calculating the phase of a complex transfer function at 10 kHz?

I need to calculate the phase of this two-port network at 10 kHz (see below). I found phasor by first finding Z_total by using the formula: Z_total(series) = Z_R + Z_C + Z_L to give: Z_total = -i/2pi ...
249 views

### Smoothing Capacitor value?

I am trying to incorporate a smoothing capacitor into a power supply for a model train set. The power supply puts out 18V pulsating DC with a max of 10 amps. The train set draws an average of 5amps ...
209 views

### How to find transfer function for this pi-filter using FACTS Method with 6 reactive elements?

Am trying to apply the FACTS method to find out the transfer function for this circuit as shown below. This is a Pi-filter circuit with all its component parasitics and also including the source and ...
1 vote
107 views

### Second Order Low Pass Filter, replacing inductor with VCCS and Capacitor

My instructor told us that we can replace an inductor in the following way. Now, I want to construct a second order low pass filter using Voltage Controlled Current Source, Capacitor, Resistor of ...
125 views

### First order RC highpass filter input capacitance

I'm trying to find the capacitive load repreented by an RC first order highpass filter. Intuitively, I tend to believe the load will not be the C series capacitance, since the capacitor is not being ...
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1 vote
270 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 ...
1 vote
152 views

### Differential Mode EMI Filter Design for DC Power Input Noises

https://www.murata.com/en-us/products/productdata/8796777775134/ENFH0008.pdf https://www.digikey.com/en/products/detail/murata-electronics/BNX022-01L/1825573 Hi everyone, I try to understand this ...
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79 views

### BLUENRG-LP BLE Antenna Design Query

I am developing a small Bluetooth Low Energy product using the BLUENRG-LP series of SoC from ST Microelectronics. For the RF matching part, I was told on their forum to just copy the design in their ...
61 views

### Parallel RLC Simulation: 0° Phase and Maximum Amplitude Don't Occur at the Same Frequency in LTspice

Context According to LAB 3L.1.1 -- Response to a Sinusoid in Learning the Art of Electronics - a Hands-On Lab Guide (by Hayes, Thomas C. and Horowitz, Paul, Cambridge University Press, 2016) 3L.1 RC ...
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### What is this following filter circuit called? (For amplifiers)

Noob here. I have a doubt on these passive low and high pass filters for amplifiers. If this is called high pass filter (which is doubled in series), then what is this filter circuit called? Here's ...
156 views

### Transient analysis of the low pass RC filter

I have designed a low pass RC filter and trying to simulate using transient analysis. I can't figure out the magnitude of the input and output waveform. What's the time delay between the input and ...
57 views

### How do I fix the output of my analog sound equalizer?

I'm new to electronics and I'm trying to build an analog sound equalizer with an TL071 as an amplifier. I have three different circuits for three different ranges (low frequencies, high frequencies ...
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
49 views

### Adding LC filter to PNP circuit

Let's say I want to add a L1C1 filter to power supply of PNP oscillator to avoid a current spikes drained from battery. In case of NPN circuits the designers usually place the L1 to Vcc rail. However, ...
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57 views

### How we change equations in passive bandpass filters?

I tried it myself, but I couldn't understand how the equation ended up in the given form. After bringing it to that form, the cutoff frequency values can be determined, but since I couldn't do that, I'...
1k views

### Why are active filters preferred over passive filters?

This question was asked to me in an interview. I replied that passive and active filters both have their merits and demerits : Unlike passive, active filters provide mechanism for gain adjustment ...
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1 vote
120 views

Theoretical question: I have seen in many analog signal circuits that the analog input pin is pulled down through a resistance. Sometimes it is also pulled up and sometimes there is a capacitor ...
81 views

### Switched-mode power supply differential vs single-ended output filter

These two filters (borrowed from here) are mathematically equivalent. Passive output filters for class D amplifiers or phase-shifted full bridge converters are normally LC filters. I've seen both in ...
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172 views

### Can we find out RLC Circuit values from just cut-off frequencies?

For example, I've passive BPF series RLC circuit with the information of lower and upper cut-off frequencies. I need to find out the values of R, L and C. Is it possible? Thanks in advance.
53 views

### How can my crossover be improved? Efficiency is too low

I have been working on redoing the crossover for a pair of Dayton audio B652 Speakers, and have just been working on it through a breadboard for practice. I bought a bunch of cheap parts from bojack ...
175 views

### Band pass filter not filtering?

I am putting together this band pass filter for a guitar project but it doesn't seem to be working. Here is the diagram and the breadboard I'm working with. There is a button there that isn't doing ...
1 vote
588 views

### How can I calculate the cut-off frequency of an RC filter?

I tred to calculate the cut-off frequency of the circuit below. When I think of two resistors as parallel and calculate them in a built-in RC filter calculator, I found a 51.0112 Hz cut-off frequency. ...
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1 vote
80 views

### RC frequency for PWM signal

I have recently read this project and would like to ask for some clarification regarding this statement/calculation: "The values shown work well an operating frequency of 1.95KHz or 13 bit ...
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1 vote
973 views

### Trouble calculating transfer function of 3rd order RC lowpass filter

I am working on simulations of a 3rd order RC filter. Cascaded first order RC lowpass X3 with: R = 100 ohms, C = 3.3 nF. When I perform the calculations for the transfer function I get a result that ...
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1 vote
121 views

### Overshoot of BJT circuit driving LEDs

It's a BJT circuit driving LEDs with a constant current and I adjust the brightness of it by sending PWM into the base of BJT. The problem is that I can see huge overshoot of LED current right after ...
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