# Tagged Questions

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### Band-Pass Filter Using High-Pass and Low-Pass at PSPICE

I am trying to create fourth poles band-pass filter.I set up this filter using texas instruments programme but I supposed to do with PSPICE.I have a crucial problem.As you can see on the screenshot, I ...
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### Why is there a lower limit on amplification for this filter design method?

I'm designing an active low-pass filter for a differential input. The input is on a ±100V scale and needs to be scaled down to the standard ±10V scale. I found this application note which describes ...
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### Low Pass Sallen-Key filter has weird response in bode plot

I have the following circuit in Multisim and am getting the Bode plot at the bottom. Could someone please explain to me what is happening? The AD8651 is listed as having a 50MHz bandwidth. Why is it ...
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### Turning on LED when input voltage has desired frequency.

I want to design a circuit that turns on an LED when the frequency of the input signal is between 950-1050 Hz using only passive elements and op amps aside from the actual LED. I have designed the ...
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### What is the advantage of non-inverting op amp high pass filter

The non-inverting op amp high-pass filter (first picture below) has a unity gain limit close to DC, while inverting op amp high-pass filter (second picture below) doesn't have such a limit. So why do ...
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### transfer function of active filters

I've been looking for some straightforward method or trick to obtain the transfer functions of active filters (like the Sallen-Key filter , the butterworth or Cauer topology etc...) since KCL or KVL ...
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### How to recognize the type of analog filter given its topology?

Having trouble to tell what kind of filter (Low-Pass, High-Pass, Band-Pass, Band-Reject(Notch) are present given a topology in cascade. In the following picture I see 3 stages, is this ok? (2 active ...
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### Differentiator Circuit

So I have a circuit like this: With the output equation as: $V_{out} = -(\frac{R_2}{R_1})\frac{s}{s+\frac{1}{R_1C}} V_{in}$ So the question is to derive the time-domain equation in terms of the ...
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### Sallen-Key filter problem

I am an Electrical Engineering student and I'm making a relay test for dad because I want to design stuff. Basically, there is an oscillator switching the relay constantly, and there is a \\$ ...
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### Audio Amplifier Op amp

I'm trying to design a circuit in which a microcontroller produces a signal and then using an amplifier drives an 8ohm speaker. I've so far used LM386, but it cannot go above 1W, which turned out to ...
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### Using Mic from 10 feet away for voice recognition

I'm trying to use a mic from 10 feet away. Background: for my senior project I would like to talk to a computer to run scripts, but I want to talk to the mic throughout the house. So I need to be ...
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### How to analyze this circuit in the time and frequency domain?

I came across this circuit in another post and started looking at the op amp filter and how to apply traditional circuit analysis ( using 1/jwc for capacitors) and couldn't derive the transfer ...
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### IR Demodulator Design

I am designing an IR demodulator circuit to replace the one shown in this question. Basically I want to demodulate a simple IR signal modulated at 32.678 kHz. I just need to know if the signal is ...
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### Detecting a 15KHz pulse with logic output

I want to build a simple and ultra low cost circuit that can detect a timed (let's say 200ms) pulse of a single sine frequency - say,15KHz. Amplitude will be around AC ~1Vp-p. Detection will give a ...
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### What does the term “slow drift” mean?

Good night everyone. I came across the term "slow drift" when reading a paper on an electronic design, and I am not quite sure what it means. The author said he used a low pass amplifier to remove ...
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### Amplifying and filtering a very low frequency signal(Bandwidth of 4Hz)

Good night, everyone. I want to amplify and filter a signal that has a bandwidth of 3.5Hz and is of the order of 5 - 40 milliVolts. I plan to amplify the signal before filtering it so as to prevent ...