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

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2answers
55 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. ...
1
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2answers
73 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
74 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 ...
0
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0answers
37 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
65 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.
1
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1answer
60 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 ...
0
votes
2answers
56 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
84 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
741 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 ...
1
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3answers
247 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 ...
3
votes
3answers
418 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
votes
2answers
95 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 ...
1
vote
1answer
218 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 ...
1
vote
1answer
171 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
votes
3answers
287 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
votes
0answers
98 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 ...
0
votes
1answer
136 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 ...
10
votes
2answers
389 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
171 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
votes
3answers
961 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 ...
1
vote
1answer
294 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 ...
0
votes
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
vote
1answer
21 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
97 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
277 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
625 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
votes
2answers
233 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
202 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
267 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
vote
2answers
401 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
151 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
votes
1answer
569 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 ...
2
votes
1answer
145 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
260 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
votes
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
1k 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
185 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
votes
1answer
490 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 ...
1
vote
1answer
219 views

Smoothing and decoupling power source input

I am transforming an old battery-only radio so I can connect it through a DC input. I found an earlier model diagram that includes the DC input (picture attached). I have connected a 18 V DC source ...
4
votes
2answers
750 views

Does my circuit need decoupling caps? [duplicate]

I have a very simple design that I'm now working on the PCB layout for. And at the moment I'm thinking about the issue of decoupling capacitors. The board is very simple and only consists of this: ...
4
votes
1answer
344 views

Why would I need AC coupling if audio inputs already do the job?

I'm transmitting data from a microcontroller to a smarphone mic input and I was suggested to use this circuit to adapt the 5v digital signal: Taken from this tutorial The way I see it R2 and R3 ...
4
votes
3answers
342 views

Can two devices share a decoupling capacitor?

I am working on a circuit that has two devices that are each supposed to have decoupling capacitors. In this case however, the devices are right next to each other, and their power supply pins are ...
2
votes
3answers
419 views

Can multiple decoupling capacitors be replaced with a single low-inductance type?

It seems to be usual practice to put in decoupling capacitors of several different values, for example 0.1uF and 1uF (or sometimes 10uF, or 0.01uF depending on the device etc). I'm wondering if there ...
4
votes
2answers
135 views

Procedure for experimentally determining decoupling capability?

I'm looking for a bullet-point list of a technique to experimentally determine a design's decoupling capability. I have a design that I'm working on that seems to be susceptible to ESD events in the ...
3
votes
1answer
114 views

Changing decoupling capacitor values

I'm building a small board that uses the MMA8453Q Freescale Accelerometer. The datasheet requires a 4.7μF decouple capacitor on the \$V_{dd}\$ pin. I only have 3.3μF or 6.8μF capacitors on ...
-1
votes
1answer
112 views

through hole or SMD capacitor for high voltage powers [closed]

When TH and SMD caps are avalilable with same spec, which one to prefer for high voltage powers.?
4
votes
3answers
3k views

Calculating the value of bypass capacitors for an amplifier

I want to know if there is a rough any ready way of calculating the capacitance required to decouple the power supply used in an amplifier. (Rough and ready because I'll be adding 30% to the value ...
1
vote
1answer
85 views

Switch (dis)connects an LDO regulator from VBATT. Where should the filter cap go?

In my system, there are several DC-DC regulators all attached to a VBATT unregulated rail. One of the regulators is the LDO shown in the picture below. The user can connect it and disconnect it from ...
17
votes
4answers
4k views

How to place decoupling capacitor in four-layer PCB?

I searched a technology document about placement of decoupling capacitors and the main idea is shown in the following picture: I think it is reasonable but do I have to put the decoupling capacitor ...
4
votes
5answers
912 views

Do I need filtering caps for a USB power supply?

I'm pulling 5V from USB for testing an IC. Should I put a capacitor in there to filter the power supply, or will it already be steady coming from the laptop? I don't have access to an oscilloscope, ...