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

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2answers
62 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, ...
-1
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2answers
72 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 ...
2
votes
2answers
71 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
106 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 ...
2
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2answers
133 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)? ...
10
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5answers
2k 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
61 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
63 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
48 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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0answers
63 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) ...
0
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1answer
46 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
36 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 ...
2
votes
2answers
119 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. ...
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vote
2answers
145 views

LM7805 followed by LD1117-3.3

The LM7805 datasheet recommends a 0.33uF cap on the input and a 0.1uF cap on the output. The LD1117-3.3 datasheet recommends a 0.1uF cap on the input and a 10uF cap on the output. I am building a ...
0
votes
1answer
110 views

Floating vs Grounded Source, and Decoupling Capacitors

I am confused about the following: in my lab, we all run electromagnets off of pretty beefy power supplies. Everyone else grounds their supply. Mine is floating. I do not have even a remotely good ...
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0answers
42 views

Shift register HC164 sensitivity issue

I am controlling 5 shift registers (74HC164) from TI's cc3200 launchpad. I am clocking the data using GPIO pin and controlling LEDs though it. But my shift register is giving weird results. It gives ...
0
votes
1answer
67 views

What is a tank capacitor?

This is from a microchip datasheet What is a tank capacitor ? It doesn't sound like a tank circuit because why would they use "capacitor" and not the other element in the tank.
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1answer
62 views

Understanding the capacitors in an op amp circuit

I am a computer programmer forced to make some circuits for a Langmuir probe our lab is making (the main task is programming the analytic software on the computer, but I have to make a basic amplifier ...
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2answers
65 views

Is there a way to fix a unsoldered SMD decoupling capacitor?

I'm rather a newbie regarding electronics but I came here to seek for a simple response. I realized that a electronic appliance I have doesn't work anymore. I tried to investigate the issue and found ...
3
votes
1answer
92 views

PCB Short Issue

I recently designed two boards and had them manufactured for a project I am working on. Before I soldered any components, I checked the continuity of some of my connections and discovered that there ...
10
votes
1answer
799 views

Decoupling capacitor with resistor in series

I am looking over a datasheet, and I saw something that puzzled me. Why is there a 1 ohm resistor (R2) in series with the capacitor? This is a power rail, so I'll assume it is a decoupling ...
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3answers
291 views

Why does my circuit work with ceramic capacitors but not electrolytic?

I had used some capacitors as decoupling capacitors for my USB powered device. Due to some chip issues, this resulted in using three 47 uF capacitors. I used electrolytic capacitors. Three in ...
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3answers
501 views

Layout of decoupling capacitors

So I've been attempting to create my first development board and layout. I'm first working on the decoupling capacitors, power and ground portions of the layout. The MCU I'm trying to properly ...
0
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2answers
112 views

Use expensive or inexpensive capacitor for decoupling

I'm in the middle of a project to create a small development board using a 100Mhz Cortex M4 MCU and have to buy some decoupling SMT capacitors. I've found the following options: Cheap 10 cent from ...
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1answer
330 views

Minimal circuit for ARM STM32F411

I'm trying to determine what a "minimal" circuit is to get an STM32F411 processor running and able to blink an LED. I wish to use the internal PLL and no external crystal at this point. I've looked ...
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1answer
243 views

LC filter and ferrite bead

Suppose I've a circuit that is affected by EMI noises that have a freq. less than 80khz and noises above 2ghz. I want to cut off this noise freq. before they reach my ICs. The circuit is powered by 5 ...
7
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3answers
400 views

Protecting microcontroller from inductive loads

I'm working on a project where I will be controlling a variety of loads (relay, solenoid, motor) from an Arduino and I'd like to make sure I build in enough protection for the microcontroller and ...
0
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0answers
122 views

Use X5R 4.7uF ceramic for bulk capacitor?

The Freescale FXOS8700CQ specifies a 100nF ceramic and a 4.7uF bulk capacitor close to pin 14 (VDD). Most designs I see use a tantalum for the bulk capacitor, but I have quite a few unused 4.7uF 6.3V ...
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1answer
159 views

Decoupling Capacitor Value [duplicate]

I am taking 12V from Power card to my backplane card to use for Hard disks. I have been advised to put decaps of 330 uF on 12V supply. Can I use 220 uF or even lesser value. What is the criteria for ...
11
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2answers
489 views

Why does ST recommend 100nF decoupling caps for a 72MHz MCU? (And not 10nF)

I've been reading about decoupling caps, and I can't seem to understand why ST recommends 100nF decoupling caps on a 72MHz arm mcu. Usually 100nF decoupling caps are only effective up to about ...
2
votes
1answer
182 views

Optimal Capacitor Placement on DC/DC Convertor

I'm trying to decide on the best layout for caps on a DC/DC converter. Which of the following options (or another, unlisted option) is the best choice? GND Out plane with 5V Out going the opposite ...
11
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3answers
981 views

Parallel Capacitor Conundrum [duplicate]

I have recently taken on a project that involves improving a circuit and there is a couple of instances where there are two capacitors in parallel with each other. The values of these capacitors ...
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1answer
302 views

Decoupling Capacitor

For power pins of IC we add a decoupling capacitor, suppose a design misses the decoupling cap. Is there anything that can be done on layout to counter the missing decoupling capacitor? My first guess ...
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2answers
175 views

Using a shunt cap to create a delay - good idea? [closed]

simulate this circuit – Schematic created using CircuitLab C1 is a decoupling capacitor. If the input of U1 is experiencing undesired phase shift, can a decoupling capacitor correct the ...
1
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1answer
22 views

PCM4202 AGNDL/AGNDR connection

First, sorry if my english is not perfect. I have a question regarding AGNDL and AGNDR connectiof for PCM4202 . In the data sheet document ( figure 12, page 21) the decoupling caps are not connected ...
0
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2answers
102 views

Decoupling Capacitor - Multiple Vss pins

I'm about to start using a chip that has one positive and two ground connections - I've only used chips with one positive and one ground before. How should I attach the decoupling capacitor(s?) to ...
6
votes
2answers
323 views

Should I keep the decoupling capacitor's vias isolated from ground fills?

I'm finishing up a PCB layout which contains a 6.5 GHz ultra-wideband transceiver with a chip antenna, an ARM controller running at 72 MHz with a 12 MHz crystal, a 16 MHz SPI bus with 3 peripheral ...
7
votes
3answers
678 views

Deciding capacitor value to use in my circuit

I have a power source which supplies 1A at 5V. I am using a switching regulator which supplies 1.3A at 3.3V. The load requires a burst of 2A without reducing the voltage across it than 3.2 V for 477 ...
5
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2answers
239 views

Decoupling with multiple caps per pin. Which should be closest?

I have an Ultra Wide Band transceiver with an internal power amp. This PA has two input pins for Vdd. According to the manufacturer, each of these pins should be decoupled with three caps; 10p, ...
2
votes
1answer
229 views

Bypass/decoupling capacitor type choice [duplicate]

Having different types of capacitors (electrolytic, film, silicon, tantalum, etc.), which types would be the optimal choice for polar/non-polar pair in this common configuration: I understand the ...
0
votes
1answer
317 views

Decoupling a power supply

I'm building my first biped robot, using a Raspberry Pi as the brain. My problem is, I want to decouple the battery before I use it to power the Pi. The reason I want to decouple the battery is ...
1
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2answers
445 views

Op Amp Decoupling with a Virtual Ground

I'm designing a low-frequency op. amp. circuit that operates from a single 10V supply. I'm using a TLE2426 "rail-splitter" to generate a virtual ground, 5V above earth ground, which is used as a ...
1
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1answer
165 views

Review and question about AD9838 circuit

I have tried to come up with a schematic of using AD9838. I used the eval. board schematic and modified it to my needs. The eval. board schematic can be found on page 9 here: AD9838 eval. board ...
0
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1answer
645 views

Decoupling Arduino's power supply

I am building a replacement for dishwasher's controller that burned, using Arduino Leonardo. Arduino is powered through standard 9V AC/DC converter. Dishwasher uses quite large 220VAC electric pump ...
3
votes
1answer
155 views

Are there flaws in the reasoning behind the Zedboard bypass scheme?

There is an eval board for the Xilinx Zynq-7000 FPGA called the Zedboard. When you look at the board you will notice a very interesting pattern of bypass capacitors. The designer has a technical note ...
2
votes
1answer
293 views

Norton Equivalent of Capacitively Coupled LRC Circuit

The diagram below is a schematic representation of a microwave lumped element notch filter. The goal is to analyse the parallel LRC circuit and derive an expression for \$S_{21}(\omega)\$, where port ...
14
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3answers
1k views

Why need the capacitors be as close as possible to the device?

Just a simple question: what exactly stands behind the need for placing the capacitors as close as possible to the current consuming device's pins? Is that the inductance, resistance or maybe ...
10
votes
3answers
2k views

“two bypass/decoupling capacitors” rule?

I found many discussions on bypass capacitors and their purpose. Usually, they come as a pair of 0.1uF and 10uF. Why does it have to be a pair? Does anyone have a good reference to a paper or an ...
2
votes
4answers
194 views

When to use film capacitor

I've bought a bunch of film type capacitor as they were pretty cheap and I thought it was a good idea to get some and test them. (set here) So I'm trying to figure out what's the specific application ...
4
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1answer
552 views

Crystal, PCB Layout

I've completed a few circuit board layouts before, however this is my first time doing a layout with a oscillator/MCU. After doing some reading (via this site and datasheets) I've come up with the ...