Questions tagged [low-pass]

A low-pass filter lets lower frequencies through and blocks or reduces higher frequencies.

628 questions
Filter by
Sorted by
Tagged with
38 views

Second order low pass filter cut off frequency calculation

I found this circuit which filters an incoming pwm pulse train from a Delta-Sigma ADC to an analog value. The PWM pulse has an amplitude from 0 to 5 V and duty cycle varies from 10% to 88%. And the ...
• 99
38 views

Switching voltage divider and low pass filter combined

I have an input signal which I want to switch from 12V-5V and a low pass filter directly after that, the issue is, if there wasn't a switch I can calculate the cut-off frequency easily. In my case, ...
• 177
84 views

How to calculate a differential + common mode LPF circuit?

I'm trying to validate my understanding of a differential + common mode LPF circuit using the AK4499EX datasheet (019001308-E-00 2022/07 version, p. 47). It presents the following circuit: and its ...
110 views

Non-ideal active low pass filter for LV25P output

Hello everyone I need some help understanding the active low-pass filter below. I was told to use this circuit to filter the measurements of the output voltage of an inverter, but there is no ...
• 19
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 ...
• 31
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
• 33
81 views

How to design a 2nd order low pass filter [closed]

I have a question about second order low pass filters. I have a DC/DC power supply at 3.3 V and I would like to filter this signal to address any disturbance from 50 Hz (ideally only keep the DC ...
2k views

Why does my integrator slowly saturate to negative rail in the following configuration?

So I have the following basic integrator circuit: The input signal is a 100mVp-p square wave of 50k frequency. In this case I get a stable triangle wave output. However, when I make the amplitude ...
105 views

How can I select a common mode choke for DC/DC power conversion stages

I want to attenuate 15 MHz noise signal using a common mode choke at 5 V power lines stage of a circuit that generate digital signals with less than 100Mhz. When you use a common mode choke for a ...
• 851
65 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 ...
• 590
126 views

Is it possible to achieve a square root analog filter?

I am attempting to create a (3/2)th-order active low-pass filter circuit, with a zero[es] at ω=10000 and pole[s] at ω=100. The only way I can think to do this is to simply cascade three simple first-...
63 views

Capacitor "blocking DC" in a low pass filter [duplicate]

If we imagine a basic lowpass filter, the AC components from the non perfect DC from VIN passes the capacitor and down to ground, meanwhile "pure" DC flows to VIN. If we take a basic closed ...
1 vote
43 views

How can I calculate filter parameters between RF switch and antenna?

In the schematics en.MB1389-WL55JC-highband-E02_Schematic, there's a Pi filter following the RF switch before it links to the SMA connector for the antenna. Upon calculation, I found that the cutoff ...
• 185
28 views

Raspberry Pi DAQHAT: Overvoltage issue

I am working on development for a piece of HV test equipment, where I need to monitor the voltage output for a circuit that is actively arcing. I am measuring the voltage off of a Raspberry Pi DAQHAT (...
70 views

Should you include multiple low-pass capacitor circuits in integrated IC PCB design?

I have two circuits, one is a POE to 5V, another is an IC for LEDs. They both include capacitors between 5V and gnd. Should I include the first 5V circuit POE capacitors since it should already be ...
• 343
87 views

High R for low frequency op amp integrator

I have to design an integrator for very low frequencies (corner frequency around 0.5 Hz). Are there any reasons why I cannot choose a really high resistor value (say 5M Ohm) to keep the capacitor ...
• 107
62 views

Negative capacitance circuit without relaxation oscillations

Wikipedia gives the following circuit as a negative capacitance circuit: I was curious if I would be able to create a low-pass resistor-negative-capacitance filter, analogous to an RC low-pass filter,...
• 25.3k
60 views

PWM Low-pass filter for LCD contrast pin with a potentiometer?

As a software developer, electronic engineering isn't my strong suit, so I'm struggling to understand some simple concepts regarding this circuit. This is a unique circuit I have encountered that is ...
• 307
52 views

Low-pass filter with a load

how can be the voltage of a low-pass filter be mathematically described when a load is connected? Is it possible to ignore the effect of the load on its voltage as something like this circuit can be ...
• 149
1 vote
101 views

How to design an inductor for the output of a low-pass filter for a 10 kVA sinusoidal UPS

The problem is that I have a 10 kVA sinusoidal UPS to repair and after replacing all the IGBTs and other components, I noticed that the low-pass filter output inductor is getting very hot at around ...
• 21
4k views

Is a 100 Ω/1 nF RC low-pass filter enough to protect a microcontroller I/O pin from ESD?

While researching ESD protection on this site, I came across this question. The answer by Peter Smith contains a comment by @Ale..chenski: Just a nit pick: if you can afford 100R and 1nF to ground on ...
• 4,683
1 vote
135 views

Loss of 2nd order behavior on 2nd order low-pass filter

I have a 2nd order Sallen-Key Low-pass filter, cut-off frequency of 170Hz. When attached to a perfect source, this is the bode plot. As expected, 40dB/decade response. The low-pass filter is used as ...
• 913
128 views

Combining voltage divider, pull-down resistor and low-pass filter in analog sensor signal

I am integrating a KP236N6165 analog absolute pressure sensor from Infineon. They recommend the following circuit : My microprocessor which receives the signal uses 3.3V logic and is not 5V tolerant ...
• 179
58 views

Is it good to equalize input impedances in cascade active opamp filters?

In my design, I designed a first 2nd order high pass filter with a Sallen key cut-off frequency of 0.2Hz and an input impedance of 250kohm. Then, I designed a second-order Multiple-Feedback low pass ...
• 756
51 views

what is the purpose of the additional resistors and capacitors in the reference design of the multiple feedback fully differential low pass filter?

What is the purpose of the additional resistors and capacitors added C14 R12 R14 R13 R15 C15 in the reference design of the .second order multiple feedback fully differential low pass filter? ...
• 756
85 views

Trying to power a 12 V LED underglow system using PWM signal from dome light

I've learned a lot from the brilliant minds on this forum so far, and I think I've narrowed my original question a bit. I'm trying to create an entry light effect in my car using my LED underglow ...
• 51
118 views

strange phase behavior RC low pass filter

I have a low pass RC filter (R=12Ohm, C = 22µF) Which is showing some strange behavior in the phase shift. The cutoff frequency is around 600Hz, as calculated. But the phase shift goes to -45° only at ...
166 views

Non-standard low-pass filter design

While experimenting with various low-pass filter topologies (audio application), I came up with the following design: simulate this circuit – Schematic created using CircuitLab It seems to ...
• 181
1 vote
86 views

Purpose of this resistor in a low-pass filter

I found this filter configuration on one of older soundcards: simulate this circuit – Schematic created using CircuitLab V1 here is the DAC output with a positive voltage offset. What is the ...
• 181
1 vote
153 views

How much gain I am getting and with the 2 stage transistor amplifier attached with a Global NFB [duplicate]

This is just a direct manual solving directly subtituting values in a formula with disregard to temp etc. Sorry for the incomplete information here are the goals of this: "gain of 100≤Av≤130 and ...
• 23
331 views

Is this transistor amplifier with low pass filter correct? How should I measure the gain and frequency range?

My goal is a gain of 100-130 and a frequency range of 1-10 kHz.
• 23
100 views

Differential DAC filter capacitor options

The standard output filter for a DAC with a differential voltage output looks this way: simulate this circuit – Schematic created using CircuitLab However, some DACs have this filter ...
• 181
124 views

RC-filter transfer function confusion

simulate this circuit – Schematic created using CircuitLab I have a question about the transfer function of the above RC-lowpass filter. If I switch places of the capacitor and the resistor to ...
• 29
1 vote
47 views

Sallen-Key filter with input signal attenuation

I want to reduce input signal amplitude before it gets to the low pass filter by 6dB. I could use MFB topology for K<1, but that would invert the phase. Is there a solution that keeps the phase? ...
• 181
69 views

Trouble understanding resulting bode plot while getting hands on filter design

Recently tried to get hands on filter design, I tried to design à simple low-pass RC filter as shown here. simulate this circuit – Schematic created using CircuitLab Cutoff frequency must be \\$\...
• 1
90 views

Non-constant active filter gain

I designed an amplifier using an instrumentation amplifier and an operational amplifier. Here, I used a 2 Hz high pass and 100 Hz multi feedback low pass filter, but I could not get the efficiency I ...
115 views

Problems with output signal of a 2nd order low pass Sallen Key filter for an electret microphone

I'm having problems with a small circuit based on the amplification of a audio signal received by an electret microphone. It goes to a 2nd order Sallen Key low pass filter circuit with an ...
73 views

LTC 2065 is not working between 2 V - 4 V power supply

I'm having a problem with the LTC2065 operational amplifier design. I use a 3.3V supply as I show in the picture, and after boosting my input signal I make it oscillate at 1.8V using a 1.8V virtual ...
128 views

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?
1 vote
100 views

Resonant circuit in class C amplifier

Questions What is the better option when maximum efficiency of class C amplifier is needed: LC circuit between VCC and drain of amplifier + low pass filter RF choke and low pass filter simulate ...
• 292
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 ...
• 15
131 views

Connecting low-pass filtered output of one comparator into a second comparator

I have the following situation: I have a signal with periodic, short (~2ns), ~1.5V pulses spaced ~10-20ns apart. I would like to detect when the pulses disappear, i.e. when there is no pulse for ~1us ...
• 433
1 vote
56 views

Trying to make a glorified aux splitter, but it won't work

I have a project due in a couple of months, and decided I want to make a aux splitter where you can control the volume of left and right on two inputs and get a single output, kind of like a mixing ...
532 views

How to improve the performance of my low pass filter design

Goal: I am designing a low-noise, 8-pole, low pass filter to use in the output stage of a lock in amplifier. The filter needs to attenuate wide-band noise and a doubled carrier frequency in the range ...
185 views

Are RC /CR - Highpass filter the same?

I‘m quite new to electrical engineering and one of the tasks is to showcase and plot an CR high pass filter. I am familiar with RC HP filters but this is new to me. Just changing the order of the ...
125 views

Can't derive transfer function of RC filter with load

I am trying to go along with an example on a simple RC filter with load in a book called Practical electronics for inventors. simulate this circuit – Schematic created using CircuitLab Although ...
• 87
83 views

Is there a reason to use different sets of resistor values in the 2 stages of a butterworth LPF?

I needed a LPF for my design so I used Filter Design Tool from AD to generate one. The generated circuit includes 2 sets of resistors of different values, which I find inconvenient. Is there a reason ...
• 41
maybe a stupid question. But let us say we have a ideal LPF filter like this: $$H\left(j\omega \right)=\begin{cases}1&-\omega _m<\omega <\omega _m\\ 0&else\end{cases}$$ If I shift it , ...