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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Why is superheterodyning better than direct conversion?

What is the advantage of having the extra stage of IF, extra local oscillator and extra filtering stage and amplification. It just seems like more work and circuitry. Surely the direct conversion to ...
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2answers
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“Top coupling” in VHF bandpass filter

I am looking at a filter design in the ARRL handbook for radio communications. It is a bandpass filter designed to pass 144Mhz with a bandwidth of around 12Mhz. The solid line represents a shield to ...
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How to generate this kind of filter?

I've been trying to understand this exercise proposed by my teacher. He asked us to find a combination of 2 ideal filters to generate a filter within the conditions of the image below. (That means, ...
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2answers
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Designing a circuit from a transfer function

I have this transfer function of a bandpass filter with 2 poles and 2 zeros: $$ H(s)= 10^{-0.8} \frac{\left( \dfrac{s}{10} +1 \right) \left( \dfrac{s}{100.000} +1 \right)} {\left( \dfrac{s}{100} +1 \...
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640 views

Picking the right opamp

I've been designing some active bandpass filters and, while in simulations it works great with ideal op amps, I'm not sure how to go about picking an op amp from a distributor. Obviously there are an ...
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1answer
385 views

Twin-T filter decay rate (drum circuit)

I'm building a Twin-T active bandpass filter as shown on this schematic: simulate this circuit – Schematic created using CircuitLab My aim is to build a simple drum-like synthesizer that ...
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3answers
250 views

Order of the filter

I can't seem to figure out the order of the filter. With the knowledge i have, "The order of the filter depends on how much change there is in the (20x)dB/decade in the amplitude response." If it ...
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2answers
415 views

Designing 4th order Butterworth Multiple feedback bandpass filter

I'm trying to design a 4th order Butterworth bandpass filter using Multiple feedback topology. The design requirements I am trying to achieve for this filter are; Q factor = 10, Av = 11, fc = 100kHz ,...
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4answers
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Why is center frequency of a bandpass filter is given by the geometric average of the two cutoff frequencies?

In electronic communication systems, there is a concept called center frequency. A bandpass filter has upper cutoff and lower cutoff frequencies. Center frequency supposed to be in the middle of these....
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1answer
392 views

Are these two circuits the same?

Are these rwo circuits the same considering the right hand sides of them where it is parallel for the C&R and C&L(meaning the way i should obtain the frequency response? And for the longer ...
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2answers
121 views

What are the differences between active bandpass filter topologies?

I want to use a narrow band active bandpass filter but I found generally 2 topologies as seen below. What are the differences between them?
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2answers
374 views

Parametric Equalizer with State Variable Filter

I'm new to this forum but hope to get some answers to a project I'm working on. I'm trying to build an parametric equalizer with several bands (5 Bass-Bands, 3 Middle-Bands, 3 High-Bands). In the ...
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2answers
129 views

Band Pass Filter for musical note separation

I have a school project that i need to separate musical notes with filters at least i thought that i can do it with band pass filter, here are the results These are the resistor and capacitor values ...
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2answers
358 views

Pole/Zero plot is the same for passive and active (w/ gain) bandpass filter, why?

I have designed an active inverting bandpass filter, and when comparing its pole zero plot to a passive bandpass fitler with the same cutoff frequencys, the pole zero plot is exactly the same, even ...
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0answers
64 views

Designing an audio amplifier, problems with bandpass filter

I am trying to build a Audio amplifier for a university project, I think that most of my circuit is done but I have an issue with my filter as my sine signal is not symmetrical after filtering to ...
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3answers
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Analysing a band pass sallen key filter

I'm trying to understand the transfer function of the band pass sallen key filter, which looks like: With the following circuit: How can I analyse it to get the transfer function? Thanks for any ...
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2answers
951 views

Filter for radio receivers

I am in need of an intermediate frequency (IF filter) for somewhere around 200 Khz as intermediate frequency. However, I know just the bare minimum of filter design ( learnt all that a couple of days ...
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2answers
938 views

LTSpice Transconductance Amplifier Simulation

I'm trying to simulate a band-pass transconductance amplifier in LTSpice, which looks like this: I used the recommendations of this post - https://electronics.stackexchange.com/a/278870/87695 - and ...
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1answer
360 views

Sallen-key second order bandpass filter low frequency response

I have designed a Sallen-Key bandpass filter with a centre frequency of 5000 Hz, a Q factor of 2 and an H0 of 5. I am trying to figure out why it responds as seen here to square wave with a ...
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2answers
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Do narrow-band single-chip bandpass filters for audio frequencies exist?

I am looking for a single-chip implementation of a bandpass filter for audio frequencies, but unsure if they even exist. All the filters I've seen seem to be at least in hundred KHz range. So my ...
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3answers
107 views

Low capacitance value capacitors in LC bandpass filter

I am going to try to build a Butterworth LC bandpass filter. However, using some online calculators result in some very low value capacitors (sub-1pF). I am thinking that the performance will not be ...
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3answers
66 views

Differential filters: high pass, low pass, band pass

I am looking to use a band pass filter in an EMG circuit design using the differential signals you receive from an op amp (differential/instrumentation). I have been looking for what is the proper way ...
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2answers
119 views

Construction of a Band reject filter

I'm trying to construct something like the band reject filter on the bode graph below. I know that I could make this by using four different filters and adding them up (low pass filter + high ...
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1answer
69 views

Why is the input reflection signal very weak?

I built a PCB filter in Class "Band-pass" with center frequency of 2.4 GHz. The board has two SMA's (input 1 & output 2). S(1,2) looks like this: The frequency is good, However, the attenuation ...
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1answer
79 views

Parallel RLC bandpass filter Bandwidth incorrect

I have been trying to create a bandpass filter with the cut-off frequency at \$\mathrm{200Hz}\$ and \$\mathrm{4800Hz}\$ I have managed to get the centre frequency to \$\mathrm{2500Hz}\$. The bandwidth ...
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1answer
140 views

Passive band-pass filter conceptual analysis

I'm trying to chain a high-pass filter and a low-pass passive filter together to form a band pass filter to illustrate how you can combine filters together, but I'm having issues trying to understand ...
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1answer
63 views

Designing a Band Pass Filter

I need a band pass filter that only accepts frequencies from 1000 to 1400 Hz and then toggles the transistor. It has to work from .1 Vpp to 1 Vpp and rejects anything else. I have been testing this ...
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2answers
254 views

Active band pass filter that looks like a sallen–Key topology filter

I was using the Analog Devices design Wizzard in order to design a band pass filter with theese characteristics: Gain : 23 dB Passband: -3dB at 15 KHz Stopband: -40dB at 40 KHz The filter has 4 ...
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1answer
54 views

Band Pass Filter Equivalent Components

I am designing a very simple first-order RC band pass filter with cutoff frequencies \$f_l = 0.5 MHz\$ and \$f_h = 4.5MHz\$. I have it pictured below (I'm using 5Spice): This filter acts the way I ...
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1answer
171 views

Fourth-order bandpass filter Bessel - I can not solve the final part (math accounts)

With the previous gain function you calculated, design a Bessel fourth-order bandpass filter with center frequency \$f0 = 10 kHz\$ and bandwidth \$Bf = f0/10\$. I did the calculations with the ...
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1answer
256 views

Problems with implementation of a band-stop filter on an MCU (dsPIC) using fixed-point arithmetic

I'm trying to implement a band-stop (notch) filter on a microcontroller dsPIC33EP64GS506 to filter out a 100 Hz component from ...
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2answers
887 views

Band-pass filter doesn't work

simulate this circuit – Schematic created using CircuitLab I designed this as it would pass frequencies between 400-600 Hz. But it passes every single frequency anyway. What is the problem?
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2answers
729 views

Second Order Bandpass Filter vs Second Order High Pass and Low Pass in Series

Is using a second order bandpass filter less effective than using a second order high pass filter and a second order low pass filter one after the other? I tried a bandpass filter to filter out ...
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1answer
746 views

Advice on 4th-Order Bandpass Filter

I am trying to design a 4th-Order bandpass filter with the following specifications; centre frequency 30 MHz, bandwidth 5 MHz and of course minimising loss. I present my current design below which I ...
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1answer
234 views

Single ended active bandpass filter

I've designed an active bandpass filter based on the one described in this article http://www.bu.edu/eng/courses/ek307/documents/ActiveFilterNotes.pdf (section 13.3.4). However, I want to use a single ...
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1answer
191 views

First-order analog active bandpass filter with variable center frequency

I've thought about designing an active first-order bandpass filter with variable center frequency and fixed bandwidth, using OpAmps, as a project for an Applied Electronics class. My first try was to ...
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0answers
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AC voltage through a capacitor

I've built a band pass filter to detect speed using a radar motion detector (IPM-165 http://nic.ath.cx/PDF/sensors/radar/CDM324-doppler/InnoSenT/InnoSenT_application_note_III_11_06.pdf). Using PSpice ...
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1answer
71 views

Grounding oscilloscope probe effects

I have built an active band-pass filter on a breadboard with the use of an MC33078p op amp. Gain is 32 on paper. When I apply the AC signal to the circuit, 18.1mV P-P and 660kHz, the oscilloscope ...
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4answers
252 views

Filter-Amplifier circuit for Low Voltage I/P circuitry

I'm designing my first ever circuit for a hobby project. I've a sensor that outputs in mV (1 to 2) and a controller with ADC. The ADC is 16 bits, VDDA = 3.0 V, Temp = 25 °C, fADCK = 1.0 MHz. Since the ...
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3answers
108 views

Band pass filter implementation using 741 op amp

My assignment for a school project on Circuit Theory, is to construct a Band Pass Filter at least 3rd order with a stop band around 20kHz. First things first, I need to design the circuit. I have to ...
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4answers
148 views

Completely different circuit response with 1000kΩ than with 1MΩ resistance

I have the following circuit (a band-pass filter) and I cannot understand what's the difference of a 1000kΩ resistance to a 1MΩ as seen here: With R223 = 1000k, my circuit outputs the expected ...
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4answers
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LCR circuit with squarewave input: Why does the output take a decreasing amplitude through each cycle?

I understand a square-wave will be made up of a sum of sine waves in the form $$\frac{1}{n}sin(nf_0)$$ So when a squarewave is input to a LCR circut designed to be a bandpass filter, it will ...
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1answer
96 views

Digitally selectable filter

I have asked a similar question but I did not get an answer, as it was too specific. So I will build on it but make it a bit more broad spectrum. I would like to make a digitally selectable BPF using ...
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Tradeoffs for creating higher order butterworth filters

I am working on a bandpass filter to filter the output from a hydrophone. This is my first time designing a filter and using a cookbook from TI, I built a 4th order Butterworth filter with two partial ...
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2answers
507 views

Transfer function of a bandpass

i was doing some homework and one thing I had to do was to derivate the transfer function of a given bandPass. I have done it myself but i dont know if it is correct nor if i followed the right path / ...
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6answers
651 views

Can a filter change the frequency of the input signal?

I am given a square wave with Vmin = 0V and Vmax=5V , T(period)=8ms and duty cycle 25%. I am asked to find the properties(low cutoff , high cutoff , bandwidth) of a band pass filter that will make the ...
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1answer
86 views

How could I design a circuit for a solar panel so that it only produces output from a red laser?

I'm designing a little laser tag system with some arduino's as a little project for Christmas break and I'm having trouble figuring out how to make my solar panel receive information from my laser ...
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2answers
111 views

Transfer Function Derivation

Where did the following transfer function come from? \$H(s) = -H_o\frac{\frac{\omega_o}{Q}s}{s^2 +\frac{\omega_o}{Q}s + \omega_o^2}\$ \$H_o\$ is the gain at resonant frequency. I'm told it ...
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1answer
165 views

Audio Equalizer LTSpice Simulation

First, I'd like to say i'm not experienced on circuits, but i'm doing my best to learn. I'm trying to create an audio equalizer which is capable of amplifying low frequencies (20Hz-200Hz), mid ...
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1answer
128 views

Ultrasonic transducer actual bandwidth for filtering

I have a pair of ultrasonic transducers with a "Thick Resonant frequency" of 975 kHz ±30kHz according to the data sheet. I did a frequency sweep test where I could see that they performed best at a ...