Questions tagged [filter]

A filter selectively processes input signals in frequency- or time-domain.

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3answers
119 views

Failed to use a low pass filter in order to convert PWM input to digital output

I want to convert a servo control signal to a digital 5V or 0V output. This is the format of my PWM signal: The different thing is my input pulse width will be either 1ms (minimum) or 2ms (maximum.) ...
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2answers
128 views

EMI Signature in electronics

What do we mean by EMI Signature? (Both theoretically and physically speaking)
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2answers
221 views

Trying to implement a digital IIR filter why is this happening?

hope everyone is staying safe. I am trying to implement a digital filter that I made from a continuous transfer function onto a STM32 microcontroller. Using the CMSIS DSP functions found here ...
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1answer
62 views

Why do reverse Bessel polynomials give rise to flat group delay in Bessel filters

I know that a Bessel filter has a maximal number of derivatives of the group delay at 0 equal to 0. I have never seen an account of what feature of reverse Bessel polynomials makes this so. Any ...
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1answer
128 views

Comparator hysteresis input signal filter

I need to heavily low pass filter an input to a hysteresis comparator, but due to the fact that R1 is one of the components setting the hysteresis, I can't add additional RC-circuits in series with it....
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2answers
80 views

Detecting small AC current signal generated by phototransistor

I'm trying to detect a small AC signal (~10kHz) generated by a phototransistor on a magnitude of 10nA~1uA using the following circuit by converting the signal to voltage signal first and then filter ...
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2answers
126 views

How Can I Design a Non-Inverting Active High Pass Filter?

All the active filters I've found 0n books and google are inverting type (i.e. input signal is applied at the negative input pin of the op-amp). I thought if I apply the input signal at the positive ...
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32 views
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I needed to find the minimal order of Chebyshev low pass filter for given dB and rad/s

Is the work ok and which one do I take the smaller value or the bigger one?
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2answers
87 views

Bessel LC Ladder Filter

I'm having trouble determining the value of the parameters of a LC Ladder Filter Consider the available tables for designing second-order lowpass ladder filters (series first) with a Bessel response. ...
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1answer
33 views

Total Harmonic Distortion fundamental frequency clarification

I have a voltage controlled amplifier that I would like to calculate the THD of using the power dissipated at the (resistive) load. My question is: if the input voltage frequency is 100Hz, would I use ...
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3answers
100 views

Location of input for negative feeback bandpass filter

I came across a reference design on a TI application imaged here: It is clear to me that there is a bandpass filter on the negative loopback branch of the amplier. However, from the few electronics ...
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1answer
147 views

Would my Audio LED display circuit work?

Would this circuit work? It's supposed to display the frequencies of the audio signal connected using LEDs by driving them with an LM358 Op-Amp. Edit: fixed the reverse polarity of U7 Edit 2: I made a ...
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1answer
446 views

How to do low pass filtering on a differential signal

If I have a differential signal on a pair of wires then how would I do a simple RC low pass filter on this differential signal?
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1answer
95 views

Designing a Chebyshev filter: am I getting the order wrong?

I'm solving the following problem: Consider the design of a Chebyshev lowpass filter with 3 dB DC gain, a passband limited to 1 kHz with a maximum ripple of 3 dB, and a stopband characterized by AS = ...
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0answers
122 views

RC filter design for ADS1115 (ADC) input

I am using an ADS1115 for measuring analog DC voltage with range of 0-5V. The ADS1115 datasheet mentions that an anti-aliasing filter is connected at the input to limit the effect of aliasing during ...
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0answers
31 views

Is this circuit a Sallen & Key biquad?

So I came up with the following filter to analyze: My first thought was that this reminded me of a Sallen & Key biquadratic section. However I'm having trouble identifying each component. Taking ...
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0answers
50 views

Question about filter transformation

I'm studying filters. In particular, I'm studying low-pass to high-pass filter transformation. I know that you only need to design an equivalent normalized low-pass filter and then, by using a ...
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1answer
62 views

Not getting expected band pass filter response

I am trying to make a LTE signal repeater and trying to filter all other signals except the band 3 (869 - 894 MHz) This is what I am getting: This is the circuit: ...
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1answer
121 views

KHN biquad: why does LTSPICE plot a wrong phase plot for bandpass filter?

I'm studying the KHN biquadratic section and its outputs to obtain a lowpass filter, a highpass filter and a bandpass filter. I simulated the filter using Mathematica and obtained the following plots, ...
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1answer
70 views

Transfer function of a filter: where is my mistake?

So, I'm trying to derive the transfer function of the following circuit: with $$R_L=3R$$ So my attempt was to treat the circuit as 3 cascaded blocks, obtaining the following transfer functions: $$\...
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1answer
107 views

Isolated DC-DC common mode choke without shunt?

I was reading a page on the Recom site (https://recom-power.com/en/rec-n-very-low-noise-filter-for-isolated-dc!sdc-converters-46.html?3) where they devised a filter setup to achieve very low noise on ...
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1answer
165 views

What is the difference between a lock-in amplifier and a superheterodyne receiver?

I apologize in advance if the answer is obvious to many of you. I was looking at some block diagrams of lock-in amplifiers the other day, and I found them to be very similar to superheterodyne ...
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2answers
153 views

Isolated DC-DC coupling capacitor location?

For a coupling capacitor across the isolation barrier of a DC-DC converter to provide a return path due to the parasitic capacitance in the transformer, there seems to be many different configuration ...
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1answer
49 views

when should I use a tuned amplifier circuit compared to a LCR bandpass circuit?

I am reading Microelectronic Circuits by Sedra and Smith. When should I use a tuned amplifier circuit compared to a LCR bandpass circuit? The text does not explain it well.
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1answer
208 views

How to calculate Pi filter for RF with PCB antenna - Nordic nRF52832

I have finished the layout of a bluetooth beacon based on SoC nRF52832 of Nordic, there is a Pi filter between the IC pin and the antenna that use the AN043 drawing of Texas. AN043: https://www.ti.com/...
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1answer
78 views

Input filter on DC-DC converter when it is the only load on a source?

Many app notes recommend placing an LC filter on the input of a buck converter to stop switching noise travelling back and thereby affecting other parts of the circuitry. But in the scenario where ...
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1answer
66 views

In need for high variable capacitance

I am constructing a Chebishev or Butterworth audio filter (low and high pass), but I need to have all parameters highly adjustable - especially Fo and Q. For this purpose i would need to be able to ...
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1answer
110 views

How to avoid false detection when using IR object detection circuit?

I have a circuit to demodulate 2KHz Infrared pulsed light which is generated by 555 timer IC and its output drives an IR transmitter circuit, which is received by IR receiver located 10 cm apart which ...
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2answers
37 views

Error in the minimum value of the operational amplifier output

I designed a circuit to control the speed of a 24V coller. For this I used the operational amplifier TCA0372DW. As I am going to control the output voltage through ...
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2answers
262 views

Low Pass Filter to Isolate DC component

I have a question based on low pass filtering. If I input a signal to this low pass filter, why does the output file have an AC (of very low frequency). The input signal is$$ v_i(t) = 2 + sin(2*pi*...
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2answers
125 views

How does a comparator based crystal oscillator work?

I'm a newbie here. Now I want to design an oscillator circuit to drive QCM-Sensor. Then I have found a circuit from the datasheet of comparator LT1671. It looks just like a relaxation oscillator with ...
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1answer
98 views

Finding the transfer function of a opamp circuit with 3 opamps

I have the following circuit: I know that \$\text{sig}_+\$ is a voltage that is \$n\$ times bigger than the voltage at \$\text{sig}_-\$. Question: If \$R_g\$ is a coil with the value \$63\space\text{...
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0answers
76 views

Unusually clean 5 kHz noise from BLDC motor

The noise does seem to pulsate but I'm not sure how I'd go about measuring the beat frequency. I'm driving this thing with 2 L293D (works fine with just one, heats up a bit though,) and feeding a ...
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1answer
80 views

Realization of network function and positive real function

I just studied 'network realizibility theory' from 'Franklin F.kuo's ' book and it mainly talks about postive real functions from start to finish and to me what I understand that for a function to be ...
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1answer
192 views

Diode in RC Filter

Is a diode ever used in an RC filter in the configuration below to stop charge from the capacitor flowing back to the source when it falls below the cap voltage (kind of like a peak detector)? Or why ...
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0answers
70 views

Unexpected noise at low pass filtered output

I am trying to capture and filter a PPG signal using a simple phototransistor and an IR led. I have hooked the emitter to a Bessel low pass filter so as to get rid of high frequency signals. Below is ...
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1answer
79 views

Only detect the phase of a sinusoid multiplexed with other sinusoids of different frequencies

Is there an easy way to detect the phase of a sinusoid that has been added to other sinudoids of different frequencies (through a frequency-division scheme) without using a superheterodyne receiver ...
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1answer
89 views

Can anyone identify what this smd component is?

It’s on a Pentax camera lens. I know it’s made by Murata. Believe there are six terminals.
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3answers
85 views

Multiplexing analog signals

I am designing a system to measure voltages from bio-potential sources and feed them into an ADC after filtering and amplification. The source has the following charactristics: amplitudes are in 10's ...
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1answer
69 views

LC Power filter not achieving modelled attenuation

I am testing an LC power filter and my real world measurements of high frequency (~1.5Mhz) switching spikes show that the attenuation is not remotely close to what my design model suggested. Situation ...
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1answer
119 views

CAN Split Termination Capacitor Calculation

I'm trying to use the split termination on a CAN bus, but I'm a bit confused about the calculation for the split termination capacitor. It is described in Figure 10 in the Texas Instruments app note ...
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4answers
1k views

How can I prevent my IR sensor from sensing the sunlight?

I want to use an IR sensor for object detection. An LED will be turned on if an object is detected. But because of sunlight, it's malfunctioning (i.e. always getting logic 1). So, how do I omit the ...
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1answer
60 views

Capacitor Placements

I have been studying the effects of using capacitors in different locations and one I have come across is split caps across a signal output. I've re-created the design in LTSPICE and screen-cap'd it: ...
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1answer
91 views

What are non-reciprocal bandpass filters?

I am not an electrical engineer. I have come to know about a term called as "Non-reciprocal Bandpass filters" which seems to be useful to me. Here are some links to the papers (unfortunately ...
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3answers
388 views

How does load resistance affect RC low pass filter?

I am building a low pass filter. This is the equation I'm using to calculate what frequencies I want to pass though, but I have a couple questions on details. $$ f_c = \frac{1}{2\pi RC} $$ What goes ...
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1answer
110 views

Transfer function and characteristic equation

I have the following network (page 805, example 14.5, Agarwal & Lang, Foundations of Analog and Digital Circuits): The associated transfer function for \$i_z, v_z\$ is \$ H(s) = \frac{I_z (s)}{...
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1answer
64 views

How to take my differential filter and design it for a different frequency and impedance?

I have a board with this differential PI filter: simulate this circuit – Schematic created using CircuitLab Say it's designed to pass signals with frequency X and bandwidth B1, and now I want ...
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2answers
81 views

Is LC filter at ESC input a good idea?

A wall climbing robot's controller board distributes power to a 150W brushless suction motor, 2x 30W brushless wheel motors and precious digital electronics (Intel NUC + STM32), the latter is ...
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1answer
64 views

How would I test if my low pass filter works on a remote FPGA?

I am making an example low pass FIR filter design to go on an Intel FPGA. I have an idea about how I'll test it via simulation (by having the input be a sum of sine waves, and the cutoff frequency be ...

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