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

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High value ceramic capacitors?

In a project, I am using the PTN78020H power supply, and it has a recommended circuit (from the datasheet linked above) that looks like this: Now on the input, it requests a massive 4 x 4.7uF ...
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3answers
76 views

Decoupling Capacitor (High Frequency Spike)

Wondering if anyone could help me rectify my understanding of decoupling capacitors and their role in suppressing high frequency voltage spikes (particularly increases in supply voltage). Similar ...
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210 views

Is it possible to de-cap a ceramic capacitor

Would it be possible to remove the case from a ceramic capacitor ? Like the ones surrounding the IC in this picture?
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1answer
63 views

How to choose MLCC cap values for power supply decoupling?

I've read that it's best to use several MLCC caps with different values to filter out as much the varied frequency noise as possible. On the output of the voltage regulator, I see some noise in the ...
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1answer
39 views

Use of decoupling/bypass capacitors for LED controller

My current circuit diagram The typical application schematic, Figure 17 (page 20), shows the usage of the 10uF and 0.1uF capacitors for the power circuitry. However Figure 16 (page 19), shows the ...
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3answers
547 views

Why decoupling capacitors used for power rails should be very close to the IC pins?

I read many experts here recommend the caps (usually 100nF ones) as close to the power and ground pins as possible. Why do they have to be soldered very near to the pins? And I used the term ...
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1answer
88 views

What is the purpose of resistance & capacitance in parallel to Load ( refer ckt )

What is the purpose of resistance & capacitance in parallel to Load ( refer ckt ) ? As per my understanding these capacitor & resistor is for filtration purpose ( kindly clarify the same) . ...
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2answers
64 views

Decoupling a Microcontroller/Development Board Design

Im trying to design a broad purpose microcontroller board (developement board?) to send off to a fab house to then use in future projects. The micro being used is an ATtiny861A. Referring to the ...
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38 views

Clarification on decoupling capacitors placement

I've seen a lot of conflicting advice regarding FPGA decoupling capacitors and decoupling in general and wanted to double check that I'm doing it correctly. So I'm directly connecting the power pins ...
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98 views

Capacitors near MCU VCC pins

I am planing my first MCU board and this MCU has several pins that need VCC (3.3V). My friend suggested that I put capacitors 0.1uF near every VCC pin to remove disturbances. But if these pins are ...
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2answers
72 views

Using a DC-DC boost converter to run a stepper motror through a chopper drive

I am attempting to use a DC-DC boost converter to step up a 7.2V battery to 24V to run a stepper motor, however, I am unsuccessful in doing so. I have tested my stepper using a DC power supply set ...
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1answer
82 views

Decoupling capacitors design [duplicate]

When designing decoupling capacitors why there are always parallel capacitors arrangements with decreasing values? It seems a redundancy to have this kind of configuration because the equivalent ...
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2answers
102 views

Is it ok to put decoupling cap over analog input of amplifier?

I'm designing a single sided board for a bridge audio amplifier based on TDA2005 (Datasheet). My circuit is the same as the one in Figure 3 in this datasheet. Schematic bellow: Here is a partial ...
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68 views

Mysterious Voltage Bias

I'm designing a color organ. My circuit so far: Quick description: Input signal is .2V pk-pk. Voltage after amp is 4V pk-pk. 2N7000 needs 2V to turn on, so it should turn on when the frequency I want ...
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0answers
73 views

Decoupling caps near ICs, but how much near? [duplicate]

I always read about decoupling CAPs should be near to MCU pins, but how much near? If we are talking about very small caps of 0201 dimensions, wich distance is good from MCU power pin? Look at this ...
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2answers
38 views

Decoupling capacitors for TLC5917

For a project involving driving a bunch of LEDs we are using TLC5917 driver IC's (datasheet). I read up upon decoupling and smoothing capacitors, but I am uncertain if and how we should use them. We ...
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4answers
192 views

Why there is no decoupling capacitors in analog IC

Here is a CMOS two stage amplifier. As you can see there is no decoupling capacitor at all. Also I don't see decoupling capacitors that are used in CMOS integrated circuits. Could you explain why? ...
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1answer
24 views

Capacitor Derating vs Impedance Curve

I need to find a ceramic cap to bypass certain freq on the power plane. Since voltage can affect the capacitance (voltage derating), and if we consider the impedance vs freq curve (V-shaped curve), ...
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1answer
64 views

Choosing decoupling caps

I know there are other questions on this site about decoupling, but I do not feel they accurately cover the full decision process. I am interested in knowing the decisions that go into choosing ...
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1answer
53 views

How to place decoupling Capacitors in a star ground design?

I am in the process of routing a star-grounded amplifier pcb and wondered on how to connect the decoupling capacitors. As I see it I have two choices: Connect the ground of the capacitors directly ...
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1answer
86 views

Aluminum Electrolytic Decoupling Capacitors

It is obvious to me that decoupling capacitors are necessary in proper circuit design. I also realize that different types of capacitors can be more useful depending on the application. However, I ...
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1answer
64 views

CMOS Gate and Coupling Noise from Loose Wires

I am currently working on this small circuit which as you can see, has to level shift a 3.3v 1Hz PPS signal into a 5v pulse. Everything is marvelous when I measure the level shifted pulse with ...
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2answers
158 views

Why use decoupling capacitor with Servo S2309S and how does it work?

I read the following statements in Arduino Projects Book, explaining about the use of decoupling capacitor in a circuit connected to a servo. When a servo motor starts to move, it draws more ...
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45 views

What is the correct order and setup of AC coupling capacitor and line driver? [duplicate]

When I use an AC coupling cap along with a balance line driver, what is the correct setup? What happens when I omit the resistor in the following schematics? Is it neccessary? simulate this ...
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1answer
103 views

Power circuit with several voltage regulators — design rules

Please, share your professional rules you follow when designing a circuit with several voltage regulators (for example 5V, -5V, +2.5V, -2.5V, 3.3V). It`s understandable and can be read in datasheet ...
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2answers
872 views

Why is it usually the case that the negative rail for ICs needs more decoupling capacitance (has worse PSRR) than the positive rail?

That the premise in the question seems to hold can be seen from various sources, including: comparing the datasheets of various clones of LM317 and LM337 (too many to list, but generally the ...
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66 views

Do I need a decoupling cap for a line buffer gate?

The data sheet does not say anything about the decoupling capacitors for this buffer gate. Would it be correct to assume that no caps needed? Please, explain.
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1k views

Why don't decoupling/bypass capacitors need resistors to perform their function, like regular filters?

Why don't decoupling/bypass capacitors need resistors to perform their function, like regular filters? Is it because the stray resistance of copper traces is enough to filter, along with the ...
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1answer
104 views

Capacitor grounded between 2 resistors

This is part of a segment of a design I came up with using schmitt triggers as relaxation oscillators. The picture below shows the 4 possible states of the circuit at any given time. Basically, the ...
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1answer
90 views

Can decoupling capacitors be doubled up? Xbee + VR both have them

I'm using an MCP1700 low-dropout voltage regulator to power an XBee separately from my other Arduino circuit, because it can use up to 215mA all on its own. There are 1uF decoupling caps on both the ...
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2answers
191 views

Which capacitor for DC blocking in audio applications?

Which capacitor (electrolytic, film, ceramic) do you use for DC blocking in audio applications? From what I have seen most people use electrolytic capacitors. But, also from power decoupling theory ...
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1answer
129 views

which of these is more efficient for AC coupling

In the beginning I was using the circuit (at the bottom) to separate the AC from the DC ( the second order filter ) which in fact is just a second order high pass filter and the DC is a zero Hz ...
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3answers
152 views

Help with understanding strange capacitor configuration arrangement

I am on a chapter of my electronics beginner’s book where the author talks about the PICAXE microcontroller. One of the first things the author mentions in this chapter is to make sure that the PICAXE ...
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0answers
59 views

AVR decoupling capacitors in 64kHz switching power supply

I am working on a compact variable switching power supply (sepic topology) that is controlled by an Atmega328p microcontroller. The unit is powered by li batteries at 3.7 volts. Everything works ...
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1answer
90 views

Power rail decoupling caps for analog circuitry

First off, the terminology I'm using could be complete rubbish - I'm still learning I have a mixed signal board for measuring bio-signals. The 4 layer board will have a split ground plane, analog ...
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1answer
338 views

Thermal pads under IC, how to place vias without soldermask / Decoupling question

I'm looking for a good solution on how to design a thermal pad that is good for solderpaste assembly. PCB fab that I'm using can't place any soldermask on vias like in this example: And I'm not ...
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1answer
103 views

This is a good connection for a decoupling cap on an IC?

Since I have no space on the BOT layer to place a cap near IC. I need to place a decoupling cap on the other side of the board, this is a good connection?
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2answers
94 views

Choice of bypass capacitors for PIC18F4455

Does anyone know how many and what values of bypass capacitors I need for a PIC18F4455? The datasheet does not provide any information on this and I don't want to use more than what I strictly need, ...
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2answers
92 views

Books on Bypassing, decoupling and Grounding [closed]

I am really sorry to ask this question but I am new to PCB designing and Its pretty challenging for me. The layout works in LAB but does not work well outside. I observe glitches in system. I am a ...
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2answers
88 views

Should every logic IC be power decoupled?

I've read before that "every IC" should be decoupled. I've never before bothered on gates, buffers, etc. No datasheet that I've read for those chips has ever suggested to do so, until I came across ...
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1answer
210 views

Problem understanding the operations of capacitor

So far I've learnt about some different types of capacitor arrangements , such as coupling , decoupling , bypass , filtering , and smoothing capacitor. Decoupling and bypass capacitors are the same ...
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2answers
2k views

AC-coupling capacitors for high-speed differential interfaces

Can you explain me why and where I should put AC-coupling capacitors (usually around 0.1uF) on high-speed (1...5 GHz) differential serial interfaces (like SerDes for Gigabit Ethernet SFP modules)? ...
12
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5answers
3k views

Forgot to put a via near bypass capacitor, and now the boards have been fab'd - what can I do?

I goofed and didn't notice this until the board was already fab'd and assembled. The board is an RF amplifier; the portion I have pictured is a part of the DC control pat (so no RF is nearby but we're ...
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1answer
226 views

DDR2 decoupling/bypassing - 100nF or 10nF?

I am slightly confused in deciding decoupling/bypass capacitor for DDR2 power supply pins. Some recommendations mention using 100nF and some mention using 10nF. I know that lower capacitance is more ...
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1answer
255 views

Use of RC circuit in amplifier output stage

I have to use a LM384 amp circuit (shown below) for a school project and need to explain how it works. I've read the datasheet (http://www.ti.com/lit/ds/symlink/lm384.pdf) and thus have a guess about ...
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1answer
89 views

1/4" TRS cross-coupled output with bypass capacitor. Is TRS jack wired for cross-coupled or not?

I'm a newbie. I wrote Alesis to get the specs on my mix board main out. Here is what their engineers said: The main outs are cross-couple, capacitor bypassed, single-ended output, for a TRS jacks. ...
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148 views

EMI filtering at end of a long copper wire transmitting high DC power

I have a long (20 - 50 m) copper wire for supplying DC power. One one end there is a AC-DC converter supplying 600W-1000W of power at 60V output. At the other end I have a switching type (100-140 kHz) ...
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2answers
130 views

LDO layout: position of output cap relative to load

simulate this circuit – Schematic created using CircuitLab In above figure, "LDO layout A" and "LDO layout B" are indicative PCB layouts of an LDO - focusing on its output capacitor. ...
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1answer
57 views

Small UPS for bluetooth audio device

I've got a bluetooth audio receiver in my car and am finding it annoying that it turns off immediately after the ignition is turned off. For example if we're stopped for a while I prefer to turn the ...
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2answers
628 views

How does Stitching capacitor provide shortest return current path between plane splits, as we know that it blocks DC current?

I heard that Stitching capacitors are used to provide shortest return path whenever a signal is routed along the 2 power plane splits. As we know the return current path will be right under the trace. ...