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# Power Supply Coupling

41 Threads found on edaboard.com: Power Supply Coupling

## How to design an AC coupling stage

1) what are your voltages? supply, input, output. 2) You tell us p-p voltage, but what's common-mode voltage? You might be pinned up against your power supply rail. 3) HOW are you adjusting your gain? In the diff amp? In the second stage? 4) what is your frequency? AC coupling is not going to work very well below some frequency.

## Fluctuation in Gate to Source Voltage

First thing that have to look in those high-power failures, is the PCB layout. Second have to look to the power supply (bias) filtering and decoupling, and any unwanted coupling between high power components.

## Differential Power Amplifier

How do you do load pull on a differential pair to know the optimum load impedance for the transistor? Do you just use one single transistor instead? A real design (either IC or discrete) will have some coupling between both output transistors, also a non-zero power supply impedance. So the impedance of the differential stage is d

## Buffer, selecting op-amp

Most single power supply opamp circuits DO NOT NEED a precision complicated circuit for a low resistance high current "virtual ground". Instead they use two resistors and a capacitor to make a "half the supply voltage" reference voltage for the opamp's high resistance very low current (+) input voltage reference. Then an input (...)

## What determines value of decoupling capacitor e.g when used with mic or bjt stage?

There is confusion about if the capacitor is for decoupling (filtering the power supply voltage) or coupling a signal from the output of one stage to the input of the next stage. The first post says to cancel (block) DC but pass the AC signal and correctly calls it a highpass filter so it is a coupling (...)

## Audio to led amplifier using lm358

It is easy to power the LM358 because it works with a power supply that is from 3V to 32V. You do not need a "virtual ground", instead you bias the (+) input to half the supply voltage with two or three resistors and maybe a filter capacitor. Then the input, output and feedback to ground need coupling (...)

## Why all RF designs bypass capacitors are much larger than blocking capacitor?

Bypass or decoupling capacitors are usually placed across low impedance power supply sources (~0.1 ohm). To acheive enough attenuation of noise greater the capacitor is. Blocking or coupling capacitor must have enough low reactance regarding to source and load impedances (50 ohm) not to introduce attenuation losses.

## 13.56 Mhz Power Supply

hi I need to make a 13.56Mhz power supply with about 1000 V - 2000 V output voltage.... can you give more on what is "13.56Mhz power supply"? and 1000v-2000v ? where it is reqd ?

## Bias strategy for multiple analog blocks sharing a same current reference

Either voltage or current mode bias distribution has its plusses and minuses. With voltage mode you worry about ground offsets and cross-chip VT gradients. With current mode, especially very low currents (hence high net impedance) you worry about signal coupling from digital aggressors and HF power supply noise. Which of these is worse, (...)

## Help needed for repairing the tracking in a bench dual power supply (0-30v, 0-3A)

Dear all, I get hold on a 30 V 3A dual bench power supply Selectronic SL-1731SB, which seems to be the same as the Velleman PS23023, and may some other ones. Both canals are OK, but when I coupled them in series, the coupling is totally wrong example Tracking not activated : A : 5.4 V B: 10.3 V Tracking activated : A :25 V (...)

## Increasing the RF 433 Mhz transmitter range

1st check output power, and supply current. The collector should be twice the supply voltage p-p when On. Can you increase power with battery voltage? . Then fix coupling cap to antenna with a much smaller value to tune impedance to antenna and resonate at 450MHz. L2 is required for this. what is the load (...)

## Calculating SNR of a Matched filter

Noise Sources: Internal Random noise in resistors and transistors Mixer noise Undesired cross-coupling noise power supply noise External EMI, Co-channel, Adjacent channel, cosmic noise, power Line transients etc. SNR= Signal power/Noise power Det

## Wifi Signal Coupling to Analog

Can you shield one of them ??Or both ??? The single practical solution that you may apply.. Picks may also come from power supply if they share the same supply lines. Ferrite beads will cutt-off the interference. Grounds are also important if they share some ground lines ..

## Power Supply for X-Ray Tube

Hello Everyone, Project I currently working is about a power supply for powering X-Ray tube. I would like to get more information about this topic and some help from you guys, if you are so kind. I apologize for my bad English. So, my goal is to build a power supply with max. output voltage 100 - 120 (...)

## Power line communication coupling circuit

Hi All, am designing power line communication light control device using PL3170 please any one tell me how to interface this to AC(230V) supply, Thanks in Advance, Kingssk

## VCC Coupling capacitors Reverse Polarity

I would like to add here a special warning regarding tantalum capacitors: They may burn violently, and cause fire hazard, and also emit toxic fumes, if they are failing either due to over-voltage or reversal. That happens very easily, if the power supply has sufficient current capacity! Therefore: If you "misuse" aluminum electrolytic capacit

## How to properly de-coupling power supply with long cable.

Hi All, I need to feed the board power supply via a 3-meter cable(dc power supply is generating on the mother board). I just wonder how can we calculate a suitable de-coupling capacitor value in this situation? We always use a big enough cap and low esr type but is there any proper way to calculate the (...)

## meaning of coupling and types of it

Under 1 (above) there is also inductive coupling. this is very popular at RF, where a tuned circuit has to be used, an additional few turns of wire around your main tuning inductor, and you have an impedance match and DC isolation. Most power supply units use inductive coupling with transformers to isolate the circuits from (...)

## Power supply OR-ing subcircuit

You may be concerned with line transients coupling into your DC, so current limiting with TVS OVP is recommended. For OR'ing DC power, I would think "high man win's " diode OR'ing would be sufficient with low voltage loss (from low current ) and no need to care which is active unless you add LED monitor from non-pattery power to indicate (...)

## remove the copper from ground and power plane under the ferrite and common mode chock

May be you could avoid draw power plane under that components. But, I can´t see any problem to route ground there. +++

## can someone help me with this circuit....???

The transition npn-pnp-npn is because of the dc level of the three operating points. But the AC coupling would allow three npn as well. An advantage of this circuit is in better rejection of power supply interferences (higher power supply rejection ratio PSRR). It's a circuit, that one would demonstrate (...)

## Cascading Op-Amps suffer from oscillation

The amplifier has 400 overall gain with about 150 MHz bandwidth. It's very easy to get oscillations by unwanted coupling between input and output or through power supply. Apparently, you didn't use a suitable "RF" circuit layout. A continuous ground plane and additional supply decoupling by ferrite beads (...)

## Battery Isolation from power supply

Hey I'm working on a wireless battery charger design. So far, i have inductive coupling to power up a PLL based battery charging circuit. each circuit works fine in isolation. but when together and when the whole circuit is off, the battery back powers the rest of the circuit rendering it ON even when its supposed to be off. I want to (...)

## Help me reduce spike voltage and ring voltage frequency in flyback RCD snubber

Hi I Simulate one flyback switching power supply with this specification in Orcad 16 cadence. Vin=24 v (DC) Vout=1300 v (DC) Iout=40 mA L1=43uH L2=150mH coupling=0.99 I have a problem in snubber circuit. I want to reduce spike voltage to minimum range and reduce ring voltage frequency. is it possible? please help me to improve it.

## Splitting a single Vcc power supply into bipolar Vcc/2

What is the circuit that will be powered with plus and minus 4.5V? Post it and we will show you how to bias it so it works with only a +9V supply.

## Coupling/decoupling capacitors

Nora, Some devices draw large amounts of transient current while they are switching. These currents can have very short rise times. Because of the inductance in the PWB tracks, this causes a momentary drop in voltage at the device power terminals. A capacitor placed close to the device provides a low inductance voltage supply, thus preventing t

## RS485 communication Noise

Hi, Opto isolator will help if the noise you are seeing is due to ground coupling. You can use 6N137 type opto and you should use it at the TTL level before RS485, at the output of the Micro. You should then use an isolated power supply to power the 485 ICs and isolated section of the opto. You can derive this (...)

## Looking for materials on ac coupling of single ended input

Can any body tell material about ac coupling of single ended input (32Khz) . A capacitor in series with self biased inverter(resistor connected to in and out of the inverter) works as a ac couple circuit. I want to know how power supply noise can effect the output. And how to set the bandpass limits? Is design requirement changes with (...)

## why we don'r recommend use tri-state in the ic ??

it also has some power problem, Tri state may casue pmos&nmos open at the same time, so there is a direct paths from the supply to ground.

## Analog layout query.... pls help me to solve it

Hello Folks, I have some query related to custom Layout: 1. Why we connect all dummy pattern to Low potential ( VSS or AVSS) power supply, Why not to highest potential ( VDD or AVDD) power supply? 2. If a sensitive net ( any High frequency net) passing over dummy pattern , Will it create any problem? Should we avoid

## what circuit it this? is it a LC filter?

Hi Nathan, It just a de-coupling circuit for your power supply. To provid more clearly power for your analog IC. Best Regards, Wenye

## what are the main issues in mixed signal design in soc

the main isssue in mixed signal soc is SUBSTRATE coupling and power supply NOISE. refer some ieee papers to get to know about it

## How to decrease bandgap noise?

I think a more power dissipation has to be consumed if you want to get a low noise BandGap. And , get a high PSR to reduce the power supply coupling. In order to get low flicker noise, user large area MOS to get the reference. Add the guard ring as possible as you can to decrease the susbtrate noise (...)

## What's the purpose of regulator?

Unstable power supply voltage causes unstable signal parameters or erratic signal proccessing, unstable operation. Regulator low output resistance minimize parasitic feedback coupling through power supply line. Most digital IC's require supply voltage with tight tollerances.

## how to do level shift

For analog design: If the process is cmos , i think the soure follows can be used. If the bipolar process, the emitter follows can be used. For digital design: The 2.5v power supply has to be need, and a cross-coupling feedback is to supply what you want.

## White Noise Generator

C1 filters the power supply to the first stage. This prevents oscillations from power supply coupling. The noise of the input resistor is amplified by the transistor stages. The noise voltage is proportional to the square root of the resistance. The two parallel capacitors bypass over a wider (...)

## Question about AC Coupling

The time constant of the RC is 5 us and your signal period is 2% of this so there will be little pulse distortion. The average signal on the right is the power supply voltage. The AC component of the input gets put across the capacitor so you will get on the transistor side the same shaped waveform but with the high Vcc+0.1 and the low Vcc-0.1.

## Impedence matching of FSK output to ferrite core trans

Hi I am working on the power line communication project. I have implemented FSK modulation and demodulation using XR2206 and XR2211 respectively. I am getting 30khz and 15KHz, 5Vpp output for logic 1 and logic 0 respectively. I have also implemented the coupling circuit using ferrite core from the power supply and (...)

## Differential RF PA vs Single ended RF PA

Differential PA in IC technology are more tolerant to common mode noise through power supply and substrate coupling. The performance of a differential PA is limited in terms of high power consumption, almost double of the single stage counterpart and low dynamic range. The cot of implementing differential PA in IC technology (...)

## How to use single supply to power opamps that need dual supply?

Well i guess you mean how to use the op-amps which need dual power supply ,well for this case there is some ct. which makes dc-dc converstion so some ct take the 9v and converts it to +4V , -4V and GND ofcourse

## Low power dicrete amplifier

From your power supply limits, BJTs are the way to go if the frequency response does not need to go very low. Otherwise, the coupling capacitors and bypass capacitors will run the cost up. You may be stuck with operational amplifiers.

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