# 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 ...
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### 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 ...
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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
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### 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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### 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
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### 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 ...
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\$...
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### 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
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### 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 ...
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 ...
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 ...
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### 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 ...
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1 vote
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 ...
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, ...
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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?
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### 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 ...
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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; ...
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 ...
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 ...
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### 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'...
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### 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 ...
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 ...
1 vote
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 ...
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