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Questions tagged [band-pass]

Bandpass is an adjective that describes a type of filter or filtering process; it is to be distinguished from passband, which refers to the actual portion of affected spectrum. Hence, one might say "A dual bandpass filter has two passbands." A bandpass signal is a signal containing a band of frequencies not adjacent to zero frequency, such as a signal that comes out of a bandpass filter.

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Band Pass Filter Design Simulation

I'm trying to simulate a bandpass filter in ltspice. bandpass filter should be in the 2-5 Hz frequency range I calculated the capacitor and resistor value for this range. However, the simulation ...
AEY's user avatar
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1 answer
74 views

Equalizer circuit using low pass filter

I'm working on my circuit theory project. My goal is to make a simple 3-channel equalizer using 1 low pass filter and 2 band pass filter. Here is my circuit. Problem is, the 8kHz passive low pass ...
GL Park's user avatar
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2 answers
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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
serkan's user avatar
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3 votes
4 answers
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?
serkan's user avatar
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3 answers
141 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 ...
sozzzani's user avatar
1 vote
2 answers
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 ...
Official Pyramid's user avatar
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0 answers
74 views

Determine the transfer function for the Butterworth bandpass filter? (At the Transfer Function Factoring and Sp Substitution stage)

The Parameter $$a_{pass} = - 1dB$$ $$a_{stop} = - 20dB$$ $$f_{pass1} = 10kHz$$ $$f_{pass2} = 30kHz$$ $$f_{stop1} = 5kHz$$ $$f_{stop2} = 60kHz$$ A. Approximate Low Pass Filter Filter Ordo $$n_B = 4.29$...
SKevinAR18's user avatar
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0 answers
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 ...
Harry Furey-Soper's user avatar
1 vote
3 answers
104 views

Why is my band-pass filter self-oscillating?

I built a bi-quad filter based on the AD8054 (consist of four AD8051 op amps) following exactly the AD8051/8054 datasheet. After I power up my op-amp, the filter entered a steady self-oscillating even ...
BenjaminZ's user avatar
0 votes
1 answer
88 views

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 ...
grandslam47's user avatar
3 votes
2 answers
141 views

How is a resonant bandpass filter similar/different from a damped mass-spring oscillator? They seem to behave different in testing

Background I am using resonant bandpass filters as musical oscillators. One can excite an array of them at harmonic frequencies and given Q values for a note by, for example, running a burst of noise ...
mike's user avatar
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1 answer
115 views

Multiple Feedback Band-pass behavior at low (<1) quality factor

I'm trying to design a filter with a bandwidth of 150Hz, center frequency of approx. 60Hz, with a roll-off of 40dB/decade. I am following the design of a 2nd order Multiple Feedback Band-Pass filter ...
HFOrangefish's user avatar
1 vote
4 answers
250 views

Discrepancy between calculated and simulated cutoff frequencies of a bandpass filter

I'm trying to simulate a bandpass filter with the following components: C1 = 2 µF R1 = 100 Ω R2 = 10 kΩ C2 = 8 nF I calculated the cutoff frequencies using the following formulas: Low cutoff ...
Habib Khan's user avatar
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2 answers
93 views

Problems with photoplethysmograph circuit diagram

I made a simple circuit of photoplethysmograph (PPG). For this I used LM358 operational amplifiers, red LED, and photodiode from old PPG. In the circuit there is band-pass filter (from calculations, ...
tomass's user avatar
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1 answer
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lowpass prototype to bandpass filter

Bandpass filter with a center frequency of 10 rad/sec and bandwidth of 20 rad/sec here, wo= is mentioned as geometric frequency that's why I am confused. The solution in which picture is correct?
Arefin Shoumik's user avatar
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2 answers
308 views

Understanding my basic parallel LC circuit, theory vs results

I made a basic LC parallel circuit. 2.9 µH inductance (measured with a cheap meter) 560 nF capacitor in parallel following f = 1/((2pi)sqrt(LC)) it should resonate at 124.89 kHz, but was manually ...
cj91's user avatar
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4 answers
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Analysis of an RCL Filter Utilizing a Potentiometer as R

I am trying to calculate the parameters ζ, Q, Fo, Gain (dB), and BW of this circuit. I am confident in the following equations: Fo = 1 / (2 * π * √(L2 * C1)) ; Q = 1 / (2 * ζ) ; BW = Fo / Q R2 = R5; ...
flower.fish's user avatar
0 votes
3 answers
288 views

Why isn't the output of this Sallen-Key bandpass filter made with transistors like the output of the op amp version?

I made a transistor Sallen-Key Butterworth bandpass filter using two filter sections for each high-pass and low-pass stage. The output is different from the op amp version. I know it is possible to ...
Michael Weaser's user avatar
2 votes
0 answers
171 views

Laser detector circuit with ambient light rejection

I recently asked how to best detect dropped balls via laser detection. Someone suggested ambient light rejection by modulating the laser and then filtering the photodetector input for that signal. I ...
Raphael's user avatar
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1 answer
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'...
XcellentEEE's user avatar
0 votes
1 answer
145 views

Band-pass filter characteristic parameters and maximum gain frequency

I think I have a big conceptual gap, I hope someone can clarify things to me. The exercise asks the following: The analytic expression of the gain \$A_v\; = \; \frac{V_o (j\omega)}{V_{in} (j\omega)}\...
RitterTree's user avatar
3 votes
2 answers
335 views

Is it possible to design a compact antenna for detecting the presence of 50 Hz mains voltage at very short range?

I have a mains cable buried in the wall. I would like to permanently place a small battery powered device on the wall over the cable's location and have the device be able to detect if the cable is ...
Wossname's user avatar
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0 votes
1 answer
126 views

Filter output of a bandpass filter

The following question was asked in GATE 2014 S-1: A 10 KHz even symmetric square wave passed through bandpass filter with centre frequency at 30 KHz and 3 dB passband of 6 kHz. The filter output is: ...
Awe Kumar Jha's user avatar
0 votes
3 answers
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.
Patrem's user avatar
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5 votes
1 answer
346 views

Two bandpass filters in series, why use different voltage dividers?

I know my question is a bit broad, but I want to ask: Using the single supply configuration, why does the first stage's non-inverting input and second stage's non-inverting input use different voltage ...
poopsalot15's user avatar
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0 answers
133 views

Multiple feedback band-pass filter issue in LT Spice

For a school project, we are tasked to make a band pass filter with a center frequency of 1000 kHz, 1 MHz. Everything works fine below 1.1 MHz. In the picture below, a sine wave with a frequency of 1....
Koby Deuel's user avatar
-1 votes
2 answers
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 ...
Alexander's user avatar
-1 votes
1 answer
66 views

Baseband circuit is not working as expected

simulate this circuit – Schematic created using CircuitLab The circuit when printed on PCB, output isn't a bandpass signal as expected. When I am checking the output with CRO across output pin ...
Sreya Ghosh's user avatar
0 votes
2 answers
226 views

Design an AGC circuit for microphone using JFET

At the beginning of the circuit, I designed a 20Hz to 20kHz second-order Butterworth bandpass filter circuit, and then I tried to pass the filtered signal through an AGC circuit to achieve a smooth ...
Jeremy Wang's user avatar
2 votes
2 answers
404 views

Transfer Function of Multiple Feedback Bandpass Filter in a specific format

I've been trying to study the Multiple Feedback Bandpass Filter. I managed to find the transfer function and the natural frequency of oscillation. $$\frac{V_\text{out}}{V_\text{in}}(s) = \frac{2\...
sumato's user avatar
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2 votes
1 answer
205 views

Design of a band-pass filter with automatic gain control using a JFET

I have implemented this circuit which is supposed to do AGC and filter out the signal between 20 Hz-20 kHz, but it seems have some problems. The bandpass filter works well, but the agc circuit doesn't ...
Jeremy Wang's user avatar
0 votes
0 answers
461 views

Narrow band band-pass filter design with LM358 op-amp

I am trying to design a narrowband band-pass filter with an LM358 op-amp, single supply 0-5 V. My requirement is a gain of 30 dB at center frequency 4 kHz and 20 dB attenuation at 3 kHz and 5 kHz. I ...
Sreya Ghosh's user avatar
0 votes
3 answers
1k views

Designing an active bandpass filter and selecting R and C values

I have been assigned the task to design an active bandpass filter with a passband of 0.1 to 10 Hz. At these two frequencies, there should be an attenuation of -6dB or more. So far I have selected my ...
palacetrading's user avatar
0 votes
3 answers
621 views

How do I calculate resistor values for a second-order bandpass filter to achieve unity gain at 1 kHz?

The bandpass needs to have a bandwidth of 250 Hz with a centre frequency of 1 kHz. The values I've calculated so far are R1 = 1000 Ω, R2 = 1000 Ω, C1 = 140 nF, and C2 = 180 nF. I calculated these ...
Lexifare26's user avatar
0 votes
1 answer
193 views

Selecting R and C values for a second-order active bandpass filter

I am using the below second-order active bandpass filter in my breathing rate sensor. I need to have a passband of 0.1 to 10 Hz with -6dB attenuation at these frequencies. I am not sure what I need to ...
palacetrading's user avatar
0 votes
1 answer
69 views

I am seeing oscillation in this SK bandpass filter circuit even without any input

There is a constant 8-9 kHz oscillation without any input. Otherwise the output is as expected. The open op-amps were terminated as follows negative feedback connection made and non inverting input ...
Sreya Ghosh's user avatar
0 votes
0 answers
62 views

LC transfer function

How would I go about deriving a transfer function or expected cut-off frequencies for this LC moveable bandpass filter (wah-wah effect)?
Lexifare26's user avatar
0 votes
3 answers
1k views

4th order transfer function

I have a 4th order transfer function. Given transfer function is below. If given transfer function had been 2nd order transfer function, it would easily be factorization of transfer function like: ...
bcdyzi's user avatar
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0 votes
2 answers
116 views

Band-pass filter

How do I ensure that the output voltage is at least 20% below the input voltage in this band-pass filter if the given resistor value is 100 Ω and the input voltage is 2 V?
jbean's user avatar
  • 35
2 votes
2 answers
129 views

RLC band-pass filter

No other values should be changed in this band-pass filter except the L and C. I was trying to get a natural/resonance frequency the same as the input which is 1 kHz, and the following are the values ...
jbean's user avatar
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16 votes
2 answers
1k views

Meaning of 'Bessel Filter'

Question I'll get straight to the narrow point ahead: I'd like an expert's opinion on the appropriate use of Bessel when considering a specific 4th order bandpass design. I don't mind a more general ...
jonk's user avatar
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0 votes
5 answers
187 views

Bandpass filter frequency response not the same as the one taken from analog filter wizard

I want a band pass filter with center frequency 5.5Khz and a passband of 1kHz. I inserted that into a website and got the frequency response and the components to implement the filter: I copied the ...
Scipio's user avatar
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0 votes
1 answer
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Why isn't the frequency response of this band pass filter circuit the same as the band pass filter with an ideal op amp?

I'm trying to develop a band pass filter with center frequency 10 kHz: The frequency response doesn't look good, but when i replace the circuit above with an ideal op-amp, I have the correct response:...
Scipio's user avatar
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4 votes
1 answer
651 views

Derivation of the transfer function of a 5th-order Butterworth LC bandpass filter

I am trying to derive the transfer function of a 5th-order Butterworth LC bandpass filter as seen in the first image. Rs is the source impedance of a signal generator and RL is where a load will be ...
Hendri's user avatar
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0 answers
185 views

How to compute the cutoff frequency of a bandpass audio filter?

Much like the title says, I'm wondering how one would compute the cutoff frequency of a bandpass filter given the filter's specs, rather than the usual resistance and capacitance. In other words, how ...
Anthony K's user avatar
2 votes
3 answers
291 views

Complex transfer functions squared

Why is it true that, for a Butterworth filter, we have \$|H_n(jw)|^{2} = H_n(jw)H_n(-jw) = \frac{1}{1+w^{2n}}\$? I don't understand why the absolute value squared of this complex function has to be \$...
ludicrous's user avatar
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-1 votes
1 answer
61 views

In Cadence AWR, why do the theoretical values for components yield much lower results than the optimized values?

I used Cadence AWR Design Environment to simulate a bandpass filter from 1.6 GHz to 3.2 Ghz, in both Pi and T formats. I calculated the theoretical values for each component and put them in the ...
Kuchi Yashwanth's user avatar
2 votes
1 answer
534 views

Band-pass filter simulation

Passive band-pass filter simulation on LTspice. Given: cutoff frequencies Flow= 10 kHz and Fhigh= 22 kHz. The run isn't getting me -3 dB between the pass. I calculated R and C and put them in the ...
Jessie Raya's user avatar
1 vote
0 answers
142 views

Bandpass filters using capacitively coupled series resonators

I was wondering how to decide on the gap size for capacitances. Here is the figure from Microwave Engineering by Pozar: I can calculate the B values, θs and other related stuff. Furthermore, I can ...
bidon's user avatar
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2 votes
2 answers
465 views

My bode plot does not mach with calculated cut-off frequencies

I have modelled a band-pass filter, but when I calculate the cut off-frequencies and amplitude it does not match with the bode-plot. I am not able to find out what is wrong, hope that someone might ...
rawonith's user avatar

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