# Questions tagged [frequency]

How many times something happens per second, measured in Hz (Hertz).

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### Hacking ATM with its aux port [closed]

(I opened a topic about it a few minutes ago but I thought it would be better if I ask my question more properly.) I wonder if is it possible to hacking an ATM (through it's aux port) with connecting ...
25 views

### Parasitic capacitance of a chip

I know that the parasitic capacitance of a chip is pronounced Cdyn. If I apply on some scenario one the chip which will toggle the all of its transistors with two different voltages, but the frequency ...
39 views

### The criterias to select peak detector capacitance and resistance [duplicate]

edit: diode is replaced with 1n4148 While designing such a peak detector, what should be the approach of choosing C and R values? Which specs of the detector will be based on them? I assume their ...
39 views

### Question: AC Voltage and Current variables

So I know how alternating current is produced, but I'm curious to what determines the voltage and amount of current moving within the wire. Does the frequency of the alternations give more voltage/...
158 views

### Frequency response of this circuit

Im not sure how to find the frequency response ($H(jw)=V_o/Vin$) of this circuit Can anybody help please?
95 views

### How does a microcontroller provide a frequency higher than its crystal frequency? [duplicate]

I have a microcontroller which is connected to an 8MHz crystal. I have a schematic which has a QSPI flash IC connected to it whose clock is provide by the micro and happens to be 48MHz. I want to ...
63 views

### Frequency Circuit

I have seen this circuit on internet. I would like to understand what its purpose is. It seems to be related to something which is call "jitter." I have done some research about "jitter" and I think ...
87 views

### Why is the impedance zero at cutoff frequencies in a series RLC resonance circuit?

I see that, in many derivations in the frequency analysis of series RLC circuits, $X_L - X_c = R$ or $Xc - X_L = R$ is considered at lower and higher cutoff frequencies. So does that mean that the ...
43 views

### “Trace Max Hold” function in spectrum analyzer

I have seen my professor doing a measurement with the spectrum analyzer in which he wanted to evaluate the frequency response of a bandpass filter. He used a signal generator in sweep mode from 1MHz ...
59 views

### Low Frequency EMI

I was wondering if low frequency EMI can occur with PWM or other sub MHz signals. I am aware that harmonics of these signals can generate EMI but I was wondering if the fundamental frequency can ...
65 views

### Ambiguity in the Definition of Resonance Frequency

we know that in a series LC circuit the resonance frequency is defined as that frequency in which the total impedance offered by the circuit is zero. We also know that in a parallel LC circuit the ...
136 views

### Sampling theorem clarifications

whenever the sampling theorem was explained to me, a situation of this kind was proposed to me. If we look at the previous image we will see that the condition to avoid spectral aliasing is that we ...
35 views

### Tuning Resonant Cavities

I have seen that some resonant cavities are equipped with some external screws, called tuners, which can be used to vary the resonance frequency. Can you explain me the physical reason with which to ...
91 views

### How to add value of 5e^(-25/2t)u(t) to a voltage source in LTSpice?

I want add the following value 5e^(-25/2t)u(t) as a Vin to my circuit in LTSpice. However I don't know how to do this - can someone help?
257 views

### Clock frequency divider circuit (divide by 2) using D flip flop

I was trying to implement frequency divider by 2 using D flip flop with the logic connection of ~Q to D input. I provide 2x clock frequency of 50% Duty cycle in the hardware where D flip flop is made ...
31 views

### change in ac reading relative to the frequency

I'm working on a school project, just measuring the Vrms of two different waveforms at different frequencies. The function generators output is connected directly into an oscilloscope therefore the ...
64 views

### In an automotive ECU application for STM32, what ADC modes should I use?

I am writing an application for the STM32f407-Discovery board that will use the ADCs present on it. I want to have access to all 17 of the input channels, and I will be using the HAL library to write ...
92 views

### Finding frequency of a series of pulses (3 - 60 Hz) without using a microcontroller or frequency-to-voltage converter

I came across an interesting yet challenging problem of finding the frequency of a series of pulses. The pulses can have a frequency anywhere from 1 to more than 100 Hz. The goal is to detect if the ...
1k views

### Why do most flyback converters / LED drivers operate under 100 kHz?

Most of the LED drivers and flyback converters I have come across operate in the 60-100 kHz range. Is there any particular reason behind this - example - ferrite cores not being able to handle higher ...
243 views

### How does Laplace transform include the transient response?

When we provide a sinsusoidal input, the evaluation of the solution of the differential equation head-on becomes horrendous. So we give an imaginary, complex exponential input and solve the ...
30 views

### What could potentially affect some specific LoRa frequencies among others and how to mitigate it?

I have started a small LoRaWAN network. I already have setup: 1x LoRaWAN gateway (LAIRD RG186, using EU863-870); 4x T/RH Nodes (Dragino LHT65, same standard); LoRa ...
53 views

### Voltage Measurement through Spectrum Analyzer

I have done some measurements with a Spectrum Analyzer of a square wave of 100kHz and amplitude equal to 1V. The resulting power spectral density is here shown: The highest peaks represent the odd ...
70 views

### How does relative permittivity decrease with frequency while capacitance doesn't?

As I understand, capacitance is $$\frac{\varepsilon A}{d}$$ where Īµ is the absolute permittivity. If the capacitor's dimensions are kept constant, then a change in Īµ with frequency should mean a ...
88 views

### Resistor annotated with a frequency

The LT3757 datasheet includes the following schematic: The resistor in the bottom left corner is annotated with a frequency (100kHz). What is the significance of that annotation?
5k views

### Where do overtones in a 555 generated square wave come from?

I have built a 555 oscillator and connected it to a speaker. Using an oscilloscope I adjusted the 555 to generate a 2.5kHz square wave. I then held a microphone up to the speaker and fed the input ...
22 views

### Sequential NAND Based Phase-Frequency Detector output

I'm trying to understand the output of my phase detector only for a pulse that goes from zero to one. here is my schematic: (ref is Clk_ref, and Div is Clk_out, both come from an outside circuit) ...
52 views

### what does phase really mean?

I'm new to EE, and I am reading a text book which says: Phase describes the position of the waveform relative to time 0. The a quiz asks What is the phase shift for a sine wave with the maximum ...
30 views

### comparing between different phase detectors

I implemented two architectures of phase-frequency detectors and I'm interested to compare between them. (I'm open for extra architectures that might solve problems that I'm not discussing here) I'...
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### Phase detection with non-ideal PFD

I'm trying to simulate for Phase Frequency Detector with the following implementation: and inside NAND_PFD: NOTE: the triangles on the right are inverters and not amplifiers. I'm currently ...
88 views

### approximation of a digital signal using the harmonic

I'm new to EE, still struggling in understanding some basic concepts. I'm reading a book which says about approximation: To make the shape of the analog signal look more like that of a digital signal,...
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### Why phase is the position of the waveform relative to time 0

I was reading a book which says: Phase describes the position of the waveform relative to time 0. It indicates the status of the first cycle. and below is a picture I am a little bit ...
51 views

### why nonperiodic signals still has the concept of frequency?

I'm new to EE from CS background, just a question on nonperiodic signals. I don't understand why nonperiodic signals still has the concept of frequency/frequency domain? The definition is : Period ...
47 views

### Accurate signal reconstruction

While reading through this page I came across following info: "For accurate reconstruction using sin (x)/x interpolation, your oscilloscope should have a sample rate at least 2.5 times the highest ...
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### In general, construction wise, what makes a speaker more or less sensitive to mid tones?

I bought a second hand vintage boombox and the left (full-range/'woofer') speaker has gone so I replaced both speakers with some Sony ones. The Sony ones are taken from of cabinets lying around (the ...
28 views

### What is an equation that will show RF wave characteristics?

I want to show a RF wave on a spherical grid coordinate system. How can I show the RF wave when t = time and y = magnitude? I also want to show curvilinear coordinate transitions of the RF wave ...
79 views

### Frequency compensation of a two-stages class AB amplifier

The author of the book on which I'm studying explains in depth the following "standard" two-stages op-amp: In order to deal with frequency compensation, he models each stage with a transconductance ...
104 views

### Is 1 Hz equal to 1 rotation of a motor shaft?

I'm rather new to the world of electronics but I have been trying to find the frequency of a DC motor. I've found that 1 hz is equal to 1 revolution per second, but does that refer to shaft rotation ...
608 views

### Why would an AC motor heavily shake when driven with certain frequencies?

I have an AC motor from an old TCL 160 Boxford NC Lathe, it has three wires named U V and W. I thought that incorparating the original driver to a modern control interface card would be difficult or ...
1k views

### Laptop failure due to constant fluctuation of AC frequency and voltage [closed]

I spend most of time on a boat (not on holiday :/ ) where a huge generator provides electricity. The potential problem is that the output is very dependent of the "mood" of the engine. Sometimes the ...
172 views

### Inconsistency in Values of Laplace Transformed Current when Changing Units

I was trying to convert the units of the following current in Time Domain and Complex Frequency domain (s-domain): $$i(t)=20\cdot e^{-t}H(t)\,\,\,\,\,\text{[mA,ms]}$$ Where $\text{[mA, ms]}$ ...
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### what is this type pulses called?

I was wondering what is this type of pulses is call. Is it a sin wave? I know its the result of sinusoidal pulse modulation. is it considerd a quasi-sin wave? I would like to know the name to ...
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### Power spectral density on the output of frequency modulator?

Is there a formula with which we would be able to calculate the power spectral density on the output of a frequency modulator? The information we know is that we have a receiver working in 180MHz ...
83 views

### Is it normal to be able to hear a high pitch buzz from devices that are charging?

I have noticed that in ungrounded outlets I am able to hear an almost silent high pitch sound if I plug in earphones into the device being charged. I think this is the 50 Hz electrical signal that I'...
69 views

### Frequency Sensitive Switch

A legacy product we are making uses this obsolete Frequency Sensitive Switch, Consumer Micro FX-301L. The switch is setup such that it switches on (-12V) at 2000Hz +-100Hz and switches off at 250Hz. ...
99 views

### Can I generate frequencies faster than 32 MHz with ATTINY85?

I believe I can use the 64 MHz PLL clock with PWM to toggle every cycle and thereby generate a 32 MHz square wave output on an IO pin, right? Is there a trick to generate an even higher frequency (...
185 views

### Arduino- Duty Cycle Changing When Frequency Is Increasing

Iām currently trying to increase the frequency from a pin from an Arduino using PWM. Iām using the Timer1 library as it has functions to output signals. I connected a push button to my Arduino and ...
50 views

### Complex Amplitudes and Exp'l Increase/Decrease

The following are quotes from a textbook, If S(t) is represented as a rotating phasor, the angular frequency of the phasor can be thought of as velocity at the end of the phasor. In particular ...
3k views

### Can sampling rate be a floating point number?

Suppose we have a sampling frequency for a signal of 15.5 samples/sec and we take samples for a period of 7 seconds. This means total samples are 108.5, does this make any sense? Shouldn't the ...
84 views

### If I look at a signal in its frequency domain, are there some guidelines by which I can tell how that signal looks in the time domain?

I was studying the Laplace transform and the Fourier transform, and I can't figure out if there is some intuitive way of finding out how a signal looks in the time domain if we know its frequency ...