Questions tagged [coupling]

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38 views

Filter for AC line coupling with audio signal source

I need a sharp notch filter (higher order) for the 50-60 Hz band, to be placed between AC 220/125 V power line and an audio source (not necessarily amplified), such that the input signal from the ...
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102 views

Why am I getting a random offset voltage?

I have query about the following circuit which is an enable for a regulator. This is on a 2 layer PCB. OUT goes to a Schmidt Triggered Inverter to the clock on a D-Type Flip Flop, where the output ...
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1answer
63 views

AC coupling of relay driving circuit - Driving relays using PWM

I have designed this circuit and math calculation works but looking back now I feel the cap is too small may be I am making any mistake here? Can some one explain how to chose the capacitor for AC ...
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7answers
2k views

What precisely is the numerical (or any) meaning of mutual inductance and, is it useful, representative (of something) or important?

When we consider two inductors that are magnetically coupled, we sometimes talk about mutual inductance. As an example, consider two inductors (such as 9 μH and 4 μH) that are 100% coupled and produce ...
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72 views

Resonant Transformer / Resonant Inductive Coupling

I´m trying to build a resonant transformer (or a resonant inductive coupler, I don´t know if the names fit to the topology I´m showing, anyway). The idea is to develop a high voltage on a capacitor. ...
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2answers
53 views

LED on lamp outlet flashes when switch is off - is this capacitive coupling charging the power supply? And what to do about it? [closed]

I wanted to connect an LED light chain to a lamp outlet in my house in order to turn it on and off using the wall light switch. I have dismantled the 230V to 3V power supply that was built into the ...
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0answers
28 views

I’m working with pcf7991at antenna driver ic

Just wondering if you can help me I’m trying to calculate capacitor and resistor values for a 125khz inductor coil . My coil measures 6.8 ohms. I’m not sure how to calculate the capacitor values ...
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1answer
104 views

Headphone amplifier is humming

I have built headphone amplifier kit and connected it to the output of DVD player. It works but I can hear humming. The humming is present only when DVD is connected. There is no groundig of the boxes ...
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1answer
114 views

Backwards compatibility of PCIe AC coupling capacitors

The PCIe base spec mentions that platforms operating only at 2.5GT/s or 5GT/s may use AC coupling capacitors in the 75nF-265nF and that platforms supporting 8GT/s and above must use 176nF-265nF. ...
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1answer
106 views

Why there is capacitor in series in high speed designs like SGMII?

Why we are connecting capacitor in series in high speed designs like SGMII. If it is to remove DC voltages, why we are not using on other signals like I2C, SPI and so on. What is the major purpose. ...
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23 views

Mutual inductance and coupling coefficient

I need to know how I calculate the coupling coefficient and mutual inductance in series-parallel (SP) topology in wireless power transfer system work at a resonant frequency of 6.78 Mhz
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1answer
60 views

Can someone explain the dependence of coupling coefficient to inductance value to me? It seems counter intuitive

According to the formula \$K=M/\sqrt{L_1 L_2}\$, it seems that k is inversely proportional to the inductance values of the two coils. However, it seems to me that a coupling between two 2uH inductor ...
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1answer
55 views

How do terminate the coax shield of AC coupled LVDS signal? (isolated grounds)

I have an LVDS clock signal that goes to several PCB cards. Frequency: 100Hz --> 20MHz I am going to use a fan out IC to supply each card with it's own buffered CLK signal; I am not going do a '...
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1answer
64 views

How to pass a signal over isolator with only one side powered?

I have a system composed of a 230VAC zone isolated from a human contact zone with a 7.5mm 2k5 space. On the human side there is a dry contact switch: I am searching for a less than 1€ solution to ...
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0answers
43 views

Coupled inductors formula

Suppose we have this circuit: simulate this circuit – Schematic created using CircuitLab According to the dot notation rule the current :The convention is that current entering a transformer at ...
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1answer
69 views

Op-amp offset voltage and capacitive coupling

About the circuit above, I can't understand from the row "VA=2Vos". If that's because most of the voltage between 1K ohm resistor and capacitor is on 1K ohm then I can't understand why VA ...
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2answers
68 views

Best way to connect coax along a microstrip

I have an open-ended (stripped, if needed) coaxial cable that I would like to use to insert a signal into a microstrip. The circuit (operating at ca. 18 GHz) however, is made in a way where I can't ...
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0answers
45 views

PLC (Power Line Communication) data line coupling to speakers

I have a PLC (Power Line Communication) to provide internet thorugh cable to all rooms. The problem I have is that this internet data is coupled to the speakers. I can hear like a "noise" (...
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1answer
84 views

Unkown DC offset of an isolation amplifier circuit design

I am designing an isolation amplifier that consists of the following blocks: A comparator which produces a PWM signal A coupling capacitor that achieves galvanic isolation A voltage follower that ...
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0answers
11 views

Coupled current in shield in a tube from a transient surge

If a shielded cable (B) is running inside the centre of a tubular structure (A), how is the coupled current from a surge estimated in the shield? I am trying to figure out how the coupled current ...
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1answer
46 views

Regarding Magnetic coupled circuit

Here, all the initial conditions are : i1(0-)=0A and i2(0-)=0A When t≥0, the current i1(t) and i2(t) starts flowing. From my assumption, steady state value of i1(t) is 10A but what happens to i2(t)? ...
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53 views

Output AC coupling: upper limit or lower limit?

I bought a DC2900A board for my project. In its datasheet it is stated: The maximum repetition rate of the pulsed laser should be 100kHz. The DC2900A repetition rate is limited by the output AC ...
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0answers
60 views

Why are the coupling capacitors needed in this DCM converter?

I have a 48V power supply which needs to be converted to a 12V output. I want to achieve this by using the DCM2322 dc/dc converter. In the Datasheet the following recommended circuit is given: My ...
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1answer
80 views

Understanding of coupling coefficient and power transfer efficiency

I am a bit confused about my derivation to get power efficiency from the coupling coefficient. The coupling coefficient \$k=M/\sqrt{L_1L_2}\$. $$ V_2=M\frac{dI_1}{dt}=L_2\frac{dI_2}{dt}\\ V_1=M\frac{...
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1answer
187 views

Location of AC coupling capacitors

I am trying to decide location of AC coupling capacitors between FPGA and PHY SGMII interface and datasheets of neither part has any useful information. I've read some notes, like this one from Dr. ...
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2answers
66 views

Oscilloscope probe coupling [duplicate]

I am using this buck converter. Schematic: Buck Converter Specifications : Input Voltage - 18V to 32V Switching Frequency - 300kHz Output Voltage 9V Load Current - 0mA to 200mA Maximum. When ...
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4answers
334 views

Roles of the coupling and bypass capacitors in a CE transistor

I wonder what the purpose of the coupling capacitors and the bypass capacitors are and the type of effect each capacitor has on the circuit. As I've understood it, you use coupling capacitors to block ...
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2answers
49 views

What is the right way to measure K on an inductor with three coils?

I have an inductor which has three coils, L1, L2, L3. In normal use L2 and L3 are connected in series, and resonated with a capacitor. L1 would then drive the tank circuit. In Spice, I need the ...
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1answer
60 views

How is this LCD controlled?

Source: https://ozhealth.com.sg/product/genial-digital-thermometer-t15-orange/ I tore down a digital thermometer today (a Genial T15), and the interface to the LCD caught my eye: although there were ...
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1answer
105 views

Why isn't capacitive coupling considered in EMC testing?

It seems like the emissions of interest in EMC testing are radiated and conducted emissions. Is this because capacitive coupling is so weak it doesn't pose a threat to other devices?
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3answers
417 views

DC-DC converter isolation capacitance return path?

For those isolated DC-DC converter bricks like seen in the photo below: The data sheet specifies an isolation capacitance in the order of picofarads. And in order to meet EMC requirements they ...
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1answer
112 views

Find the Q-factor for coils and understand weak power transfer

I built coils for wireless power transfer. Found inductance with a LRC meter. Put capacitors, hoping for a resonant frequency at 300kHz. Student assisted me with a NVA machine where a resonant ...
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22 views

"Coupling" gain-setting resistors in a single-ended source, differential amplifier?

I am working on a fully differential amplifier design that receives a single-ended differential voltage from a piezo sensor. I computed a theoretical gain and selected appropriate resistors and it ...
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2answers
95 views

AC coupling of a transistor

So we assume to have proper bias currents flowing in both of the two transistors. What is claimed by books is that a capacitive coupling will not change the bias parameters. But, we know that a ...
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0answers
404 views

Royer oscillator - frequency shifting in WPT

I am having a problem with my WPT resonant application. In my circuit modified Royer oscillator feeds LC tank. Receiver coil nearby is connected to rectifier and variable resistor. I know about ...
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2answers
115 views

EMC - conducted emissions - unused wires in cable - puzzling coupling

I am trying to understand the impact of unconnected wires in a cable for EMC conducted emissions tests. My product has a shared unshielded cable for supply and communication (I know it's bad practice....
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0answers
114 views

Where is the capacitive coupling in this adafruit soil moisture sensor?

Here is the moisture sensor: https://learn.adafruit.com/adafruit-stemma-soil-sensor-i2c-capacitive-moisture-sensor/downloads It has a large copper area insulated with soldermask that sticks in the ...
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0answers
87 views

Understanding Ac coupling in this circuit

I'm simulating the circuit below in LTspice and there's something I don't get regarding C3 and C4. Suppose the input signal is a 32 uArms 60Hz current as shown. This value multiplied by the burden ...
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0answers
112 views

How to measure capacitive coupling on pcb traces?

I have bare PCB board (6 layers) with me and I would like to see if my switching signals (60 kHz) have any effect on the sensitive current measurement lines. I just want to know if there is quick ...
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1answer
258 views

How to calculate cutoff frequency for a high pass filter in DC biasing circuit

I would like to DC bias an AC signal using a voltage divider as shown in the following schematic. I realise the bias point would be subject to noise from the power rails, but that is not a concern for ...
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1answer
115 views

Coupling coefficient of microstrip resonators

I am working in HFSS and I'm trying to determine the coupling coefficient between two microstrip resonators (k) so that I can design a filter using a certain resonator shape. I have the formula I need....
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2answers
203 views

Unintentional capacitive coupling

This question comes from text from the AOE 3rd ed. It's about unintentional capacitive coupling right after differentiators in chapter 1. I've included the text. Please read the first excerpt. That is ...
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1answer
30 views

Does DiSEqC require a DC bias?

The DiSEqC (Di[gital] S[attelite] Eq[uipment] C[ontrol] specification (bus_spec.pdf within https://www.eutelsat.com/files/PDF/DiSEqC-documentation.zip) describes a tone-based serial data bus that can ...
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3answers
158 views

Shifting level voltage of a signal

I have a signal, which can vary from 400 to 7000 Hz approximately. It is a kind of pwm signal and has the time of high level, Ton, 30 times longer than the time of low level, Toff. The shape of the ...
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3answers
253 views

Adding small AC signal to a DC current using inductive coupling

Is it possible to add a small AC current on to a DC current in a wire using inductive coupling from an external source. Or if there is another way, I want to add AC ripples to a DC current. simulate ...
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1answer
120 views

What grounding should I use for this capacitively coupled input?

I'm designing a device that will receive and digitize analog video signals. In analog video, it's recommended to capacitively couple inputs. A typical input might look like this: In this case the ...
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1answer
169 views

2n7000 used for inductively coupled load modulation apparently latched

So I've got a fairly basic circuit set up for load modulation of an inductively coupled circuit: A few notes on the above: LC's were designed for 1 MHz but work better at 950 kHz, thus the chosen ...
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4answers
718 views

AC-Coupling on Composite video

Many sources say that composite video input should be AC-coupled. Voltage levels for blank, black and white signal are also specified. How is it possible to detect these voltage levels after AC ...
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3answers
184 views

If a PEC surface completely reflects an EM wave, why doesn't an ungrounded shield work?

I was thinking about shielding and its effectiveness. An ungrounded shield doesn't work well for either inductive or capacitive coupling. However, if you think about plane wave theory, a PEC surface ...
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1answer
398 views

Coupling PCB traces

In my pcb design I have 2 triangular voltage signals with the following specs: Peak voltage = 300V Rise and fall time= 7us Freq=25kHz (assume a constant current of 0.5A) Because of the limited ...