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Questions tagged [decoupling-capacitor]

A capacitor, usually ceramic, used to provide instantaneous energy to a local circuit.

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Bias transistor for digital signal decoupling source (composite video amp)

Short question first If I want to use an emitter-follower to strengthen a signal source and I need a bias network for the transistor, how do I isolate this from the source if the source is digital? ...
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ESP32-H2 doesn't work fine when powered via external power supply and 3V3-Battery pin

I've a new ESP32-H2 that works fine as a Matter device if it is powered from USB port. When I try to power it from 3V3-Battery pin using a very reliable power supply (Keithley Model 2231A-Triple-...
M4Biz's user avatar
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ICs that share the same supply voltage

Do I need decoupling caps on each V+ pin of my I/O expanders when they're all sharing the same 5 V supply?
Rue D's user avatar
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Decoupling capacitors for operational amplifiers

when in the refence design of an amplifier (for example OPA856) we see the + sign in a capacitor schematic, does this necessarily means we should use electrolytic capacitors? If there is no positive ...
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Decoupling cap powered via ground return?

I have a new 4 layer board (Pwr/Sig, GND, GND, Pwr/Sig) that is behaving in a way I don't understand and some how "back powering" a 5v plane it shouldn't be able to. The board is in 2 ...
Neil's user avatar
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Tantalum capacitor for op amps

Normally for opamps supply voltages, it is suggested that there should be (100 nF + 2-10 uF) on the positive and negative supply pins. The second capacitor which is in range of uF should tantalum? Or ...
Andromeda's user avatar
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What is the purpose of these 10nF capacitors?

What is the purpose of these 10nF capacitors on all the ECU input pins? Image source: https://www.finjector.com/documents/647ef11579093/TKU-0261230340-.pdf, section 2.4. Error diagnosis
featherbits's user avatar
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Decoupling capacitors - adjacent pads, different capacitance requirements, shared voltage source

Background The TI TLC6983 LED driver datasheet provides decoupling capacitor recommendations for the IC and LED supply pins, in ...
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How to ensure the current passes through decoupling capacitor?

I am familiar with adding decoupling capacitors to protect input power pins of chips on PCBAs, as well as output power pins of voltage converters. Still, there is something I am not sure of. Below are ...
uz3il's user avatar
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Is it good practice to place decoupling capacitors near connector pins?

I’ve seen some notes online about placing decoupling capacitors near I/O connector pins, as well as some saying power lines of connector pins. Despite this, I feel that I haven’t often seen capacitors ...
cs_eng_516's user avatar
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Adding a capacitor between positive and negative supply pin can cause stability issue in OpAmp circuit?

I have a transimpedance amplifier designed and when I apply +/- 2V to its supply pins it is oscillating, I noticed when I apply GND to V- supply pin, it does not oscillate, so I have a little bit ...
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Decoupling capacitors for LED matrix driver

The TI TLC6983 LED driver datasheet provides decoupling capacitor recommendations for the IC supply pin, in 10 : Power Supply Recommendations: Decouple the VCC power supply voltage by placing a 0.1 ...
kando's user avatar
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How do I implement the decoupling capacitor in this diagram?

I'm following a tutorial on how to control a stepper motor, and it instructs me to place a capacitor across a 12V DC power supply, as shown at the top of the diagram. I've seen explanations for how ...
CarolusRix's user avatar
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Routing Power vs. Power plane (high frequency)

As a beginner, I'm curious about handling fast analog signals with nanosecond rise times. Do the decoupling capacitors of ICs need to recharge rapidly to supply charge effectively? Would employing a ...
Tim Buktu's user avatar
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How to stop LEDs flickering when ESP32 is connected?

I'm working on a circuit that consists of an ESP32 and a series of LEDs connected to the same power supply. My problem is that when the ESP32 is using Wi-Fi, the LEDs start to flicker: https://imgur....
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Do I need to provide a decoupling capacitor network for all the power pins of a microcontroller?

I am using PIC32CZ8110CA90208-I8MX-SL3 in my design.The power supply section is given below. You can see that it has: AVDD 1 pin VDDIO 15 pins VDDREG 3 pins Do I need to provide a separate ...
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DC bias of electrolytic capacitor

I see DC bias characteristics for ceramic capacitor where capacitance decreases with applied voltage. I am not finding the same data for electrolytic capacitors. Do electrolytic capacitor values vary ...
NICEGUY NICEGUY's user avatar
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Best decoupling capacitor part or series? [closed]

I am using motor driver, for PVDD as per datasheet I provided decoupling capacitors 100nf close to each pins (4pins) and a bulk capacitor 10uF as common both are X7R ceramic. I see some article ...
NICEGUY NICEGUY's user avatar
2 votes
1 answer
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How do chip designers determine how many decoupling capacitors are required?

When an IC designer has designed a new IC, how do they determine the necessary level of decoupling required for its power rails? Do they just take a guess, or is there a more formalised/accurate ...
Rob Gilton's user avatar
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2 answers
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Ascertaining that a BGA's decoupling capacitance is good enough

BGA parts often have a large number of power pins in the middle of the package. It is of course important to ensure that the power rail has been sufficiently capacitively decoupled. How can one go ...
Rob Gilton's user avatar
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456 views

Why don't we use decoupling capacitors for open-drain outputs?

If an IC with open-drain outputs (and hence pull-up resistors) is used, we of course put decoupling capacitors on the IC supply, but why don't we also add decoupling capacitors between the power pin ...
John Arg's user avatar
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7 answers
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How do capacitors stop voltage spikes?

In circuits like the one below, I don't understand how the capacitor can handle voltage spikes. I heard that decoupling capacitors deal with spikes by absorbing more of the voltage, but I don't ...
EskimoJones's user avatar
5 votes
4 answers
2k views

Why are smoothing capacitors useful/why do they work

Okay so from my understanding and looking at the equation for the impedance a capacitor has, the high frequency signals would be relatively easy to be sunk to ground (if the capacitor was grounded) ...
George kirby's user avatar
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How do you estimate a decent value for a decoupling capacitor? [duplicate]

I want to know how you can find a decent estimation for the value of a decoupling capacitor without the need of experimentation. I don't want an equation, I'm just wondering if there is a simple rule ...
Anish Kommireddy's user avatar
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5 answers
4k views

Why are PC motherboards covered with many large capacitors?

This is a contemporary Xeon motherboard: When I was growing up, the wisdom was that you placed a 47uF capacitor where the power leads attached to a digital PCB. Now, this seems to have been updated ...
Paul Uszak's user avatar
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Decoupling Caps Topology from Microchip MPU Datasheet

I am trying to develop a power distribution network for this device. https://ww1.microchip.com/downloads/en/DeviceDoc/MPU-SAMA5D27C-CNVAO-datasheet-60001532a.pdf I am looking at decoupling capacitor ...
Jack Frye's user avatar
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STM32F0 VDD / VDDA connected

I want to use an STM32F0x to interface a i2c sensor via USB. Reading the sensor is triggered by an interrupt. If I don't do any ADC I should be fine with connecting VDD and VDDA right? I know this ...
Piglet's user avatar
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Is it possible to measure the ac noised filtered by a bypass capacitor in an oscilloscope?

Is it possible to measure the ac noised filtered by a bypass capacitor in an oscilloscope? Because when we put the probes around the capacitor are we also not measuring the voltage around the resistor ...
NTOS Linux's user avatar
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How to test the working of a decoupling capacitor with an oscilloscope?

How can we test the working of a decoupling capacitor with an oscilloscope. I think I understood the need for a decoupling capacitor in a circuit. One of their use is to remove the noise from the ...
NTOS Linux's user avatar
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MPQ4470-AEC1 Layout guideline clarification

I am using MPQ4470-AEC1 in my design. In the datasheet page no 18 contains the layout guidelines. I have some questions about guideline no:2 and no:3 .Those guidelines are given below. Place input ...
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Alternatives for 0402 0.1 uF capacitors in custom RP2040 PCB

I've been designing my own custom RP2040 board, but with only a minimal number of components to do a UART and I2C peripheral, and no USB. However, the design guide https://datasheets.raspberrypi.com/...
Wayne Piekarski's user avatar
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1 answer
194 views

STM32F407 Heating up, the decoupling capacitors showing short to ground with multimeter but microcontroller seems working fine

I have an stm32f407 which was running okay for like a month. but now i am seeing that whenever I connect power supply the current consumption is very high and the MCU is heating up a lot. The ...
Mir Hamza's user avatar
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1 answer
101 views

Designing my own scale with 0.01 gram resolution [closed]

I'm aiming to design a weighing scale with a resolution of 0.01 grams. I'm familiar with basic electronics, but I'm not sure where to start to achieve such a high resolution. Could anyone provide ...
Lusungu Mtawali's user avatar
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Choosing capacitors for Buck Converter – How many Electrolytic, How many Ceramic?

I am working on a high-power buck converter. This converter will be powering a purely resistive load (it’s a literal resistor – a heating element). However, I am having some issues deciding how many ...
Kuba0040's user avatar
1 vote
2 answers
111 views

Decoupling Capacitor voltage Selection

In my board there are many IC's present and for all these IC's it's manufacturers specified the decoupling capacitors. When I generated my initial BOM what I observed is 99% of these capacitors are of ...
Confused's user avatar
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Decoupling capacitor package 0603 vs 0201

I am using Microchip's SAMA5D27C-D1G-CU. In the reference design all the decoupling capacitor packages are 0201. I have the same capacitor with all the specifications suggested by Microchip, except ...
Confused's user avatar
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Why are low capacitance capacitors better as decoupling capacitors?

I still can't understand the physical reason why small ceramic capacitors, when placed very close to the power pins of an IC, effectively filter out noise. And if the capacitance value is smaller, ...
WalterPH's user avatar
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Forgot to decouple RFM69HCW

I was in the middle of soldering a PCB I designed when I realized I forgot to decouple the RFM69HCW module with 0.1uF. Does anyone have any insight to how damaging this is, and if I need to redesign ...
1W0n_29's user avatar
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Decoupling capacitor high frequency impedance value

Here is frequency-impedance curve for real capacitor. The basic profile of a dip and then increase in the impedance is caused by the ESL. It is not possible to get rid of ESL and it is a non-ideal ...
quantum231's user avatar
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FPGA decoupling capacitors

FPGAs have among the largest packages and the most voltage rails. This is especially true of the high end devices e.g Stratix, Virtex Ultrascale+ e.t.c. This means a whole lot of decoupling capacitors....
quantum231's user avatar
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3 votes
3 answers
355 views

Necessary components for diy ATMega328

I am trying to build a barebones avr based circuit, based on designs i found on the internet. My questions are based on this sub-circuit: I don't plan on using a Reset button, thus S1 will be omitted....
user1584421's user avatar
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Do voltage multiplier circuits and transformerless power supplies have functional similarity? [closed]

I saw diagrams of voltage multipliers like in the picture below. To my understanding, it seems like they have the same function as transformerless but the use of a voltage multiplier is to increase ...
user avatar
3 votes
1 answer
196 views

Filtering with bypass capacitors: how to check ICs' switching frequencies?

When adding by-pass capacitors to a design, I have read that it is not enough to just place the typical 0.1 μF value and the 10 μF one; you have to check why you need those values. I mean, which are ...
Developing Electronics's user avatar
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Do you need a decoupling capacitor for an RC servo connector?

I have watched a lengthy youtube video about decoupling capacitors and how you should use them. I am in doubt if you should add decoupling capacitors in front of 3p connectors for RC servo motors such ...
bask185's user avatar
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2 votes
2 answers
113 views

Connecting bulk capacitor board via header or standoff?

I am routing a 2 board design that are stacked on the top of each other. The lower board (inverter board) contain the power transistors and a separate board contain the bulk DC-link capacitors for the ...
Eng Sam's user avatar
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1 vote
2 answers
205 views

Unstable access to external MRAM when using Nucleo STM32 H7 board

I have an asynchronous MRAM device, AS3004316 4Mb 35ns (https://pt.mouser.com/datasheet/2/1122/1Mb_32Mb_Parallel_x16_MRAM_2-1949428.pdf), connected to an STM32h743 nucleo board through the Flexible ...
Meruje's user avatar
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2 votes
2 answers
398 views

Decoupling capacitors, ideal distance between VCC and GND pins on chip based on impedance of copper trace and ground plane

I'm designing a PCB for a Mancester decoder I simulated a while back (and also asked about here) (simulation on Falstad.com), and would like to include decoupling capacitors. I have no experience ...
BipedalJoe's user avatar
5 votes
2 answers
756 views

Why should decoupling capacitors be closest to the voltage regulator?

I was reading the datasheet for the voltage regulator uA7812 to implement in my circuit and it says at page 15: Keep trace widths large enough to eliminate problematic I×R voltage drops at the input ...
ludicrous's user avatar
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1 vote
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Is a single decoupling capacitor for multiple Vdd lines adequate?

The image is taken from the RK3399 datasheet. Here you can see that a 10uF decoupling capacitor is connected to 13 VDD lines. Is it a good idea to connect one single decoupling capacitor for all lines?...
Confused's user avatar
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1 vote
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How to connect off-board Vcc+ and Vcc- to the power plane?

This is my first 4-layer design and I can't easily find a clear answer to this question. I am designing a 4 layer PCB (signal-GND-pwr-signal), where regulated +12 and -12V power is supplied through a ...
Aaron Kimball's user avatar

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