# Questions tagged [frequency]

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

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### What is the correct formula for the 3 dB frequency of an RC or LC Circuit?

Before we jump to another post where the formula is I am reading through the text book Microelectronic Circuits 8th edition by SEDRA/SMITH. In the text, they show this table. Here it shows the time ...
60 views

### Simple square wave frequency multiplier/divider

I have a square wave 0-12 V input signal that varies from 30-150 Hz, which I wish to multiply to an output square wave 0-12 V signal of 60-300 Hz. In this case, the multiplier is 2, however I ideally ...
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### Need Help Increasing PWM Frequency from 800 Hz to 8000+ Hz for DC Motor Speed Control

I'm currently developing a speed control system for a powerful 12V DC motor that pulls a heavy load. To enhance system efficiency, I need to raise the PWM frequency from the 800 Hz (PLC upper limit) ...
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### Why does a MOSFET fail on fast signals, even if they're much longer than the turn on + turn off times?

When running at a fast signal, why does the MOSFET below not turn off, even when gate voltage is well below threshold (even negative)? Although the signal is fast (7 MHz, 140 ns period) it is < 1/...
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### How can I determine how much power is in a frequency range via FFT in LTspice?

When using LTspice, I can see the FFT of a voltage. How can I see how much power is in a particular frequency band, and what portion of the total power it is? The FFT in LTspice is in dB, but it's ...
• 1,215
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### What does the standard deviation of TIE measurement tell me about my clock signal jitter?

When we take a Time Interval Error (TIE) measurement of a clock signal, we are presented with two measurement outputs, the mean error and the standard deviation. When I measured the TIE of a 32....
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### Change analogWrite() frequency using the arduino framework for SAMD51

I am using Adafruit Feather M4 Express board which has Atmel SAMD51 controller on it. I am using platformio as IDE, which lets me use this controller using the Arduino framework. I want to change the ...
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1 vote
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### How to generate a 50-100 Hz 12 Vac sine wave for audio tone from 5 VDC (PB0 pin) atmega164p microcontroller [closed]

I have programmed to ATmega 164P to make PBO high when PC1 is low. In programming, I'm adding other peripherals as well. But I am facing one issue regarding generating a tone. I have drawn low pass ...
89 views

### Oscilloscope Low Sampling at uHz Sinus Signal

I tried to measure a sinus signal at 1000 µHz with my R&S RTC1000 oscilloscope (bandwith 300 MHz). The function generator that I used was the EDU33212A. I set the T/div=100s and the oscilloscope ...
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### How to modify frequency of an analog signal [closed]

I want to create my own pcb. First step is to design my circuit. I thought about a voice modifier. So, in the breadboard I should put: a microphone (an electrostatic electret microphone) followed by ...
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### When increasing the frequency of an induction motor can't I just add a capacitor to maintain torque instead of increasing the voltage?

When increasing the speed of an induction motor if one wants to maintain the same torque, the voltage has to be increased at the same proportion as the frequency of the AC supply. This is because the ...
95 views

### Oscilloscope Total Record Samples Vs Signal Frequency

I have the oscilloscope R&S® RTC1000 at 300MHz / 2GS/s / 500Mpts (Mega Points) with 12 horizontal divisions on the screen. 1st Example: If I have a signal 1Hz the total samples that the ...
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1 vote
135 views

### Having trouble with a 555 Astable timer outputting into NPN transistor switch that controls 741 Op-Amp

I have been building a circuit that takes the output of a 555 IC and outputs it into an NPN transistor that acts as a switch to toggle a 741 Op-Amp connected to an 8 ohm, 0.5 watt speaker. I'm new to ...
118 views

### Why is the gain of the amplifier not considered in the frequency calculations? (Sedra and Smith 6th edition, Example 1.5)

In example 1.5 in Sedra & Smith 6th edition, the author's answer for item b) is 1 Mrad/s. To get this answer, the author considers the amplifier as a passive LP network and uses the time constant ...
2k views

### Changing output impedance of a logic gate to 50 ohm

I making a simple circuit to take 10 MHz output from a GPS module and calibrate a frequency counter with this 10 MHz signal. I have already found a circuit designed by radio amateur ZL2PD. Circuit ...
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1 vote
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### How to use this crystal oscillator? [closed]

I recently bought a 315Mhz crystal oscillator off of Amazon but I can’t figure out how to use it nor can I find any information online about it. The only thing I can find on them is that picture. I ...
38 views

### Difference between radio transmitter roll-off and bandwidth-time (BT) product

For any radio transmitter, the output signal will likely have a shape filter to manage bandwidth. However I am struggling to understand the relationship between a roll-off (e.g. 0.35) and a bandwidth-...
67 views

### What is minimal frequency to detect such signal? [closed]

I develop simple signal generator, to debug other devices. It sends high logic signal which has length approximately time length 64 microseconds. If i connect some device which has processor frequency,...
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### Amplitude modulation problems

I am trying to do amplitude modulation using a diode, but my circuit will not work. This is the circuit I am using: simulate this circuit – Schematic created using CircuitLab I don't know why ...
53 views

### Specific frequency filter

I want to use an insolation monitoring system that outputs different frequencies for every state. Exactly 0, 10, 20, 30, 40, 50 Hz but I want to use the 10 and 50Hz only. Is it possible to build a ...
62 views

### Animal repellent circuit for cows and goats

I want to create an animal repellent circuit for my school project but I'm having some problems designing the circuit. The circuit does not produce any sound frequency. NB: We are not allowed to use ...
45 views

### What is minimum gain crossover frequency in bode analysis?

I know gain crossover frequency at which magnitude of open loop transfer function is 0. But what is the case here for minimum Wgc?
1 vote
83 views

### Using an LT1357CN8 to amplify the signal of a 1.5 MHz frequency generator

I am working on a frequency generator to control piezoelectric transducers. I use an Arduino Uno R4 Minima to send data to an AD9833 which creates my desired sine wave up to the required 1.5 MHz. ...
77 views

### SPWM - Frequency calculation

Below is the SPWM I produced with 50 Hz sine wave and 5 kHz carrier signal. I will use the SPWM signal to drive the MOSFETs in my inverter. As it is known, duty and period are constantly changing in ...
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### Must LC resonant frequency be identical to oscillating frequency in RF circuit?

I am developing an RF circuit for 503.3 MHz. It will be an AM RF transmitter. The LC circuit I built into this circuit consists of L = 0.1 μH and C = 1 pF. The carrier frequency which carries the ...
1 vote
56 views

### ledcWriteTone leaking to other pin?

I've recently written a program that involves two blinking LEDs. I have these LEDs wired straight from the pins into GND. One is set to blink on and off on one second intervals, and the other is fed a ...
95 views

### What is the negative omega squared in this function?

I'm trying to draw a Bode plot for the transfer function, but I am confused on what the negative omega squared is supposed to be. Is it supposed to be the frequency with no phase angle? How can I get ...
1k views

### BJT as current buffer for op amp

I am working on creating a 10-20KHz 0-5V sine wave feeding a coil which would be around 450uH. At this stage I am stuck in that I can produce the sine wave using an STM32 or a DDS IC but that will not ...
146 views

### What is a simple circuit to generate TTL signal with fixed frequencies?

What is the simplest circuit that can be used to generate a 5V TTL signal with fixed frequencies such as 0.5Hz, 1Hz, 50Hz, 100Hz, 500Hz, 1kHz, 5kHz, 10kHz..?
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### Why is my LTspice simulation so different from my calculation by hand?

This is the circuit: $$V_{in} g_{m1} + \frac{V_{in}} {r_{o1}} = (V_{in} - V_o) s C - \frac{V_o} {r_{o2}}$$ $$\Rightarrow \frac{V_o} {V_{in}} = \frac{s C - g_{m1} - 1/ r_{o1}} {s C + 1/r_{o2}}$$ The ...
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### +/-10V input voltage to frequency converter

I need to convert a bipolar voltage to a frequency. Say -10 to +10V for the example. For the context this voltage is the error signal from an analog feedback loop. I have a schematics that works well ...
3k views

### Frequencies are inherently positive physical quantity.... what does it mean?

While I was going through a digital signal processing course, I came to this problem where it says that "Frequencies are inherently positive physical quantity" - Digital Signal Processing by ...
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1 vote
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### Dynamically change PWM frequency on NRF52810

I'm using a NRF52810 to control an LED load and need to ramp up PWM frequency over the span of 6 seconds, like 0-1s : 6Hz, 1-2s : 7Hz, 2-3s : 8Hz, 4-5s : 9Hz, 5-6s : 10Hz. At the moment, this is how I ...
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### Frequency meter (counter)

I am currently working on designing a circuit that should be able to measure the frequency of an input signal by giving off a value directly proportional to the frequency at the input. The circuit ...
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236 views

### How to use skin depth

Do you use skin depth to determine the minimum thickness of your conductor? In other words, if I calculate skin depth to be 200 microns at the lowest frequency, should my wire, at a minimum, be 200 ...
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### Frequency demodulation circuit

This is how I designed the frequency modulation circuit, but I cannot perform the demodulation process. It can be done with a PLL but I couldn't install it. How can I demodulate?
256 views

### Inductance of solenoid with solid metal core

Consider the solenoid/inductor like in the picture. There is an air gap between the coil and the inserted solid metal. The solid metal is from aluminum or copper (Both have a relative magnetic ...
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### Measuring magnetic fields in the 1-10 Hz range

I apologize in advance but I am a chemist just venturing into the world of electrical, so you may need to explain to me like a 5 year old. I have a chemistry project that involves the use of AC ...
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1 vote
139 views

### How does this metal detector circuit work with an AM receiver?

I do not understand how this circuit works. From Fun Electronics Projects for the Experimenter by Newton C. Braga. It is described as using the beat-frequency method to detect an object. The ...
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### Can anyone tell me what this circuit is doing? [closed]

I am reluctant to share the whole circuit due to company confidentiality, but effectively a frequency ref is inputted into Q1B. Q1a's collector is connected to 3V3 through a series of resistors and a ...
78 views

### Which frequency to consider in SPWM for a transformer, the resulting frequency or SPWM frequency?

I am build an inverter with the EGS002 board, which has a SPWM carrier frequency of 23.4 KHz. In my mind the logic is that the transformer winding, material and size should be calculated using the ...
129 views

### How to find the strongest frequency in a signal using a microcontroller/circuit?

I am trying to implement a low-power backscatter transmitter+receiver and ran into some trouble on the transmission side. Setup: My transmitter circuit sends a 50MHz wave, which the receiver circuit ...
693 views

### What is the maximum frequency for a diode if a superimposed AC sine wave on DC pass through it, and the diode stays always ON due to DC?

How can I determine if a forward biased diode (always ON) can be used to pass the full band of a superimposed AC sine wave on DC? The diode is just used as a protection device against possible reverse ...
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### Initial conditions in a circuit with two ideal transformers [closed]

I don't know how to determine initial conditions in Laplace transform for a circuit or a system of circuits with ideal transformers with neither mutual inductance nor coupling coefficient is given. I ...
130 views

### Do piezoelectric or piezoceramic sensors have a fixed resonating frequency?

I am working with a sensor which has piezos in it. I want to know what piezo resonating frequency really means. The piezo I'm using has a resonating frequency of 570kHz as mentioned on the website. ...
2k views

### Is there any way to measure sound intensity in decibels without using a microphone?

I am trying to measure sound intensity in decibels without using microphone in a home automation project. Due to privacy concerns, I don't want to use a microphone in the device. Is there any way I ...
1 vote
127 views

### How can I find the resonating frequency of a piezo crystal?

The crystal looks like in the given image I want to find the resonating frequency, whether is it variable or fixed. I find its manufacturer has not given much detail about it. Does a piezo resonate ...
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### fT and fmax of a bipolar transistor

I want to find the maximum frequency of the input voltage in a Bipolar inverter. However, I cannot seem to find any formulas or equations for it. Should calculate fT, and if so, how?
179 views

### Variable frequency sine generator

What is an simple option to generate a low freq. sine in range 10Hz to 200Hz? I tried to make a triangle and integrate it but I obtained a huge difference in amplitude as I change the triangle ...
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