Questions tagged [capacitor]

A fundamental electronic component that stores energy in an electric field, commonly used in filtering applications.

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23 views

time delay in Lumped element delay line

I was trying to analyse a lumped element-delay line by changing the frequency and measuring \$ V_{in}\$ , as shown in the graph the goal of my analysis is to find the time-delay and the attenuation ...
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235 views

Astable multivibrator: what starts the first cycle

I think I understand how the astable multivibrator works once the LEDs are blinking (cf. below), but I don't understand how the first cycle begins. I can see that at first, the 2 LEDs are on (based ...
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Capacitor for triggering negative edge J-K Flip Flop's Clock

I have some SN74LS73AN Flip-Flops which, if I understanding well, are triggered by the negative edge signal of a clock. I wish to use a simple pushbutton as a clock, and I am aware that I need a ...
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35 views

Need help to solve ESD air discharge problem

I have a PCB that failed an ESD test on 8kV air discharge. I cannot add a guard ring or remove the components near the edge of the PCB since I have very limited space. It seems because the ESD voltage ...
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1answer
72 views

Keep MOSFET open using capacitor

I'm building a circuit that stays powered for some time after an additional power source is switched off. +5V is always enabled but I only want LOAD to be powered when VCC (12V) is enabled and for ...
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2answers
59 views

Determining an equation for the current after the switches close

I know that the solution of of the form i(t) = A*sin(wt + phi), I am really confused where to start in finding A, w and phi however. Here is the circuit in question:...
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1answer
42 views

Do I need more capacitance for my crystal?

I've used the formula "CL = (C1 * C2) / (C1 + C2) + Cstray" (where C1 = C2) to calculate the capacitors I need for my board. CL is 18pF, I ballparked Cstray at 5pF, meaning I should use ...
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How do smaller capacitors filter out higher frequencies than larger values?

I commonly see 0.1 µF used on IC pins for decoupling. I occasionally see 0.01 µF and 0.001 µF capacitors used for filtering out higher frequencies. Is that incorrect, because I thought the impedance ...
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31 views

How to check for the ESD protection of the capacitors

I have this circuit I need to check whether my input capacitors C0001-c0004 are protected for ESD events. My ESD pulse spec: +/-8kV, 2kohms & 330pF. I have taken 130% of this +8kV as my ESD pulse ...
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1answer
80 views

How can an AC source be connected in parallel with a DC one (through a capacitor) in a common-collector BJT configuration?

As far as I understand, voltage sources (regardless they are AC or DC) should never be connected in parallel, since they are not ideal and one would end up charging the other. However, in the ...
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Capacitance detection circuit in LTspice

I have designed a circuit to detect ice in software LTSpice. When I did ac analysis, it shows the gain is constant from 10KHZ to 10MHZ. That means, I can detect ice during operationg the sensor with ...
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How to select the resistance value for an Arduino capacitance meter

I'm working through examples for an Arduino capacitance meter and the ones I've seen give the known resistance of the RC circuit as 10 kilohm. It's my understanding that we could use "any" ...
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73 views

Opamp with capacitive load

I've heard that opamps are not good at driving capacitive loads. Let's say I want to add an RC antialiasing filter between the opamp output and the ADC. Is 0.1uF big enough to cause trouble? Where can ...
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1answer
64 views

555 timer circuit causes spikes on power supply line - how to decouple?

I'm using a 555 timer circuit similar to this one to blink a couple of LEDs at around 1 to 30 Hz: The oscillations are causing huge spikes on the 5V supply line. There is an audio circuit running off ...
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68 views

Do capacitors provide ESD protection even if they are already charged?

I've read about ESD protection with capacitors and it seems that if one knows its limitations it could in some cases be a cheap alternative for or addition to designated ESD protection circuits. The ...
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Has anyone made a ~1pf cap on a PCB?

When you get into the single digit pF capacitors, the capacitance approaches what could be achieved with only a trace (which wouldn't be changeable, but I don't care about that). Quick calculations ...
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51 views

Placing capacitors between opposite rails in an unregulated power supply

I am making an unregulated dual rail power supply for an audio chip amp from a center tapped step down transformer and bridge wave rectifier. There are capacitors between the ground and the positive, ...
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2answers
75 views

AC-DC Powersupply voltage drop

I just bought this power supply for a project. I just went in with a multimeter to test the voltage and pins, which gives me a 20V reading as expected. However, after I remove the power supply from ...
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2answers
57 views

Is it possible to use a capacitor and a resistor to keep voltage above 3v and limit current to a certain value? [closed]

I have an RC helicopter and the electronics require a voltage of at least 3v. The electronics also have a certain max amperage which might be around 2 amps. Under high load on the brushed motor, the ...
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1answer
51 views

Problem in microphone circuit

I've placed the circuit on the breadboard and found an unexpected low-frequency noise appearing again and again. The computer microphone doesn't show this type of distortion. But my circuit is showing....
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1answer
47 views

Differential equation to describe an RC circuit with a sine wave

In this image Vin is a sine wave , sin(ωt), and I am trying to get the differential equation that I will then be able to solve. I am having troubles trying to find the current through the power supply ...
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1answer
86 views

Help identify these capacitors

Could you give me more info on these capacitors? My guess is Top = 50pF Bottom = 15000pF = 15nF Correct? What is the meaning of remaining char? Thank you!
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Parallel plate capacitor simulation

I want to simulate a parallel plate capacitor, I am using ANSYS HFSS for this purpose. I made 2 PEC sheets 50mm x 50mm. The distance between the plates is 1mm (vaccum). I need to draw a rectangle to ...
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1answer
58 views

How to size a capacitor?

I want to design a PCB with some ICs and I've read that it's recommended to use decoupling capacitors to filter out voltage spikes. There are three ICs on the PCB: Arduino NANO, nRF24l01 module and ...
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56 views

How will be the charging and the discharging of this capacitor

In the given circuit, if 230 V DC is applied at the same time when the gate is triggered, does the capacitor first charge and then discharge or only charge?
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I want to understand this audio input to LED output simple circuit

I'm a newbie in electronics. I watched a youtube video that showed how to activate LEDs using a microphone. It's project #3 at https://youtu.be/zsJ61yJhWVU?t=115 The guy built the circuit on camera ...
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47 views

MLCC capacitor - AC voltage performance

I'm planning to replace an MLCC capacitor (250 VAC voltage rate) with a capacitor MLCC (650 VDC voltage rate). Regarding the two datasheet of component I'm facing to this curve below : Can any one ...
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45 views

Preventing opamp from possible saturation maybe

I am trying to simulate a gyrator circuit for implementing capacitor as inductor in LTSpice. While simulation I am encountering the following problem : It seems that top left opamp undergoes ...
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34 views

Inductor Based on capacitor and gyrator

I was trying to implement Inductor using capacitor in Lt spice. But the circuit waveform is not steady. Also the impedance is not exactly proportional to frequency. please explain this deviation.
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23 views

Finding the capacitor value for power factor correction

I know the formula of how to find the capacitor value but id need to find the supplies value first and I don't know how to do that. I have the Is=21.60A and phase angle=43.95. question: A recent ...
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Capacitor filter optimization for ATmega32U2 board

I've been working on a project built around a ATmega32U2 with a PMW3360DMâ€T2QU optical sensor and I have some questions on where and when capacitor to ground filters are necessary. Many of the ...
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106 views

What's the role of capacitors in this circuit?

This is a followup from a previous question: Analysing signal unbalancing stage which was quite broad as it encompassed couple of things, but answer there pointed me in the right directions so I'm ...
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Question about series-connected (pseudo-nonpolar) electrolytics

Another Q&A on this site ("Ceramic caps vs electrolytic. What are the tangible differences in use?") contains good information on capacitors in general, including parameters I wasn't ...
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Having Trouble Turning a Capacitor on a Condition [closed]

for my project, I'm creating 4 way traffic lights using logic gates and ICs. I'm certain that my design should work but for some reason it's not working on tinkercad. The main thing I do is that I ...
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47 views

Help Me Identify This Capacitor

This multi-layer ceramic capacitor indicated in the picture is missing. It's next to an internal memory chip for the Nintendo Switch LITE. I need to replace it but I don't know its specs. Could you ...
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1answer
41 views

How can I tell whether an SMT/SMD Capacitor is oriented with plates horizontal or vertical?

This article talks about mounting capacitors with the electrodes parallel or perpendicular to this microstrip indicating that "By mounting the capacitor vertically, that is, with the electrodes ...
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How can I limit the slew rate of current in a battery circuit?

Let me be more specific: I have a circuit fed by a battery and charged by a charge controller and I don't know exactly what is the max slew rate of current in it, but, I can estimate conservative ...
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1answer
75 views

What is the best way to layout this ultra-low inductance capacitor with interleaved pins?

This TDK capacitor interleaves its pins to reduce inductance. For a high-pass tee filter, wouldn't I need vias to bring the negative lines off separate from the positive ones? But vias increase ...
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1answer
71 views

Unexpected (unintended) capacitor charging explanation

Please first consider the below schematic. It is the balanced output part of an existing hifi preamp. Not my design, it's confidential so I can only reproduce the relevant part. Things that might be ...
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2answers
210 views

Op amp driving large capacitive load - do I need to be careful during power off?

I have an LTC6090 high voltage amplifier, with a +140V supply, driving a 200 nF load through a 10 ohm resistor. During device power-off it's possible that the aplifier +ve rail will sink faster than ...
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45 views

Integrating and Differentiating Circuits in General and for a PID Controlller [closed]

TL;DR Why are integrator and differentiator circuits called as such, and why are PID controller constants connected in parallel? Ok, so I have just been introduced to integrating and differentiating ...
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1answer
35 views

Vary Capacitance in LTSpice

I would like to model a condenser microphone in LTSpice. This kind of microphone has a variable capacitance dependent on the incoming pressure. I know how to vary a resistor with time, but ...
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1answer
31 views

Contactor rating with capacitive load, how to compute the maximum allowed capacitance?

Considering this: simulate this circuit – Schematic created using CircuitLab V1 is a beefy battery - it will happily provide 1000A or more; RLY1 is a beefy contactor, the LEV200 series, rated ...
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108 views

What makes industrial capacitive sensors so good?

I am using a proximity sensor on a battery powered wearable sensor and maybe facing some detection issues because of a bad grounding. I am seeing detection differences between the sensor system ...
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1answer
71 views

How do I introduce impedance in an AC circuit?

Complete noob here so please bear with me. I want to know how to and how much impedance to introduce in a single phase AC circuit of 220v and 50hz so that I can bring it down to 100v. My load is an AC ...
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1answer
51 views

Time constant vs Length of Pulse in RC circuit

Reading through "The Art of Electronics", I came to a statement where the writer states that the time constant (t) of RC circuit must be many times bigger than the Length of pulse you want ...
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63 views

Double voltage in full wave rectifier

I made a simple full wave rectifier using a center tapped transformer and 2 1N4007 diodes. The DC output is around 14 volts but when I connect a 100uF capacitor with the output leads of the DC output, ...
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43 views

Change the speed of an induction motor with an additional capacitor

I have a three phase induction motor (a fan motor) that get power from a two phase power line. To start the motor I have a start capacitor. I need to change the speed of the motor to reach the 70% of ...
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1answer
76 views

How does this under voltage lockout (UVLO) work?

In my project, I need an under voltage lockout (UVLO) to connect the load electronics to the energy-storage element via a power-gating transistor when the voltage across the supercapacitor exceeds ...
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1answer
37 views

What is the limit I have to take so that the capacitance formula for concentric cylinders shows the capacitance of infinite plates per surface area?

I'm trying to figure out how to solve this problem. The formula for the capacitance of two concentric cylinders is given as \$C=2\pi\varepsilon L/ln(b/a)\$, where b is the outer radius, a is the inner ...

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