# Tagged Questions

Impedance defines the voltage/current characteristic of any dipole circuit.

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### Driver impedance of a microcontroller pin, for series termination?

Many guides instruct that digital signals should have a series resistor placed by the driver, whose resistance is equal to the line impedance (Z0) minus the driver impedance (Zd). Here is one such ...
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### How to select the right Operational Amplifier as an impedance converter?

I have a receiver circuit that is magnetically coupled via a parallel resonant circuit with the sender (similar to RFID but just one directional). I want to feed the signal into an ADC which has, ...
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### I was explaining a transistor to someone, and I realized: I don't really understand several key concepts at a low level. Help?

(Surplus story removed.) I was explaining MOSFETs, CMOS, and logic gates to someone and realized I didn't grasp some concepts as well as I thought. It culminated when he drew a single transistor, ...
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### What options do I have to measure directly impedance change (ohm) or deduce it indirectly from S-Parameters?

Basically I want to measure how impedance (Ohm) relative to Z0 (50 Ohm) waveguide is changing by varying a parameter. I currently measure the reflection coefficient S11 in a 1-port setup. Our VNA can ...
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### Influence of a magnetic field on coil impedance

If you take a coil and make a current flow through it, the coil creates a magnetic field. This field induces a voltage into the coil that produces a counter current that weakens the primary current ...
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### AC-coupled RF Microstrip routing over power plane

If I route a 433 MHz AC-coupled RF microstrip trace out of an MMIC such that it's referenced to a Power plane rather than a Ground plane, will that have a significant effect on the impedance of the ...
70 views

### Output impedance of voltage divider?

When connecting a 10S LiPo (42V) to my ADC via a voltage divider, I began wondering how to calculate the output impedance of the divider. simulate this circuit – Schematic created using ...
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### Calculation of Open loop differential gain and open loop output Impedance

I want to calculate the open loop output impedance and open loop differential gain of a discrete differential amplifier (Figure attached). Is this feasible? Here is the approach. INPUT STAGE: ...
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### Effect of metal resistivity on the characteristic impedance of microstrip line

We know that the characteristic impedance of a microstrip line is given as follows: In general the metal resistivity is so small that Z0 can be taken as sqrt(L/C). But if the metal resisitivity is ...
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### Impedence of 90° out of phase Capacitor and Inductor in parallel

I'm curious as to what the equivalent impedance would be of these two elements. Mathematically it seems that they would have infinite impedance (meaning an open circuit), but this doesn't make any ...
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### Transfer function of R and C parallel

Currently I am learning control systems. I specifically find the mathematics very hard to understand. For my exam I am practicing on this question: "Determine the transfer function of this circuit in ...
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### A question about the argument part of impedance

The definition of impedance is Z = V/I. I'm trying to understand the idea behind the argument part of the impedance concept in a capacitor. First here is what I know briefly so far: I will begin ...
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### Difference between 32 KHz clock output load vs. clock input impedance requirement

I have a WiFi chip that requires a input impedance of > 100 kohms and < 5 pF as seen in the requirements table found in the datasheet below. I'm confused if this 5 pF requirement correlates to ...
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### Circuit to measure impedance

I'm trying to make a circuit to measure impedance through a FRDM-KL25Z board. The basic idea is to use two signals to calculate the phase shift between them, and use a impedance divider to calculate ...
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### Reflections on a differential transmission line

I understand why reflections occur when there is an impedance mismatch on a single-wire transmission line. However, when we introduce a differential line, I am having trouble picturing what would ...
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### Wy are speakers rated by impedance instead of inductance?

Audio speakers contain coils which product sound by vibrating a cone. Why are speakers rated by impedance instead of inductance?
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### L293D Motor driver 'braking' using input pins

I read the following on Wikipedia: Using pins 2 and 7 ( 15 and 10) to determine motor START/STOP or PWM duties it's dangerous, since there wouldn't be high impedance outputs: Current would flow ...
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### Does the absolute sum of the elements of the imaginary part of the Y-matrix correspond to anything?

I have a simulation of a device with 4 ports (a double gated organic field-effect transistor), about which I also have some experimental data. I also made a simulation where I extracted the impedance ...
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### Different Op Amp output for battery/usb power

I'm using a micro running arduino to measure the resistance between two electrodes, connected to a dual op amp with automatic feedback control bias. The output is accurate when the circuit is powered ...
37 views

### Impedances to simplify RC circuit?

Suppose I am trying to solve the following circuit, where $V_i$ is the potential seen from the top branch to the bottom branch (which is 'grounded') and $V_o$ is the potential across $C_2$: ...
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### How to calculate the output impedance of this circuit?

This is a hybrid-pi model of a BJT, and I want to know its output impedance: simulate this circuit – Schematic created using CircuitLab I know that I should short the input ports, place ...
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### can the inductor and resistor values be found from the impedance

If the inductive impedance is given can the separate resistor and inductor values be calculated? OK The question gives the voltage supply (magnitude and frequency), power factor and current. It ...
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### Input impedance of audio amplifier, unclear from datasheet

I have a AN7190NK audio power IC. It is a amplifier for the car radio. I want to know it's input impedance. In datasheet it states that: Input impedance ZI VIN = ± 0.3 VDC 28 kOhm I don't really ...
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### Output Impedance of circuit

Please see image. Should'nt the output resistance be Rout = ro1 || ro3 rather than just soley ro3?
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### Input power with PF, impedance on transmission line and transformer

I've just had and exam (Renewable Energy) and we had a problem that I'm not sure if is correct. The answers should be simple as we haven't studied tranmission lines at all. Okay, here we go. We have ...
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### Impedance phase angle relative to?

In a simple PARALLEL RC circuit with two components of Resistor 150 Ohms and Capacitor 0.000000075F (75nF). AC supply 10V at 20,000Hz. Impedance has a phase angle of -54.7 degrees if my calculations ...
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### Build own custom USB 'regulator' adapter board to solve Desktop boot hangs with KVM

My Desktop PC hangs in the BIOS boot phase when my KVM is attached. If I unplug the USB connecting the PC to the KVM, the PC boots without hanging. If the USB of the PC is connected directly to the ...
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### Why is a shielded cable not effective with high impedance sensor?

Could some one simplify what this means? Why is the shielded cable not effective with a high impedance source/sensor?
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### Impedance matching for piezo element

I am trying to boost audio signal from around 3V to around 60V for a piezo element with a component as small as possible. I found audio transformer MET-23 that reflects 1.6 kOhm impedance on primary ...
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### What resisters for inverting op-amp should I use?

I am not an electrical engineer by any means so go easy on me here. I am simply experimenting with a speaker amplifier. My situation: I have a Clarion xc1410 4-channel amplifier with a 10k input ...
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### Power calculation and Ohm's Law for Reactance

Hi I have the following question: V = 120V, I = 10 A, I lags V by 60degrees simulate this circuit – Schematic created using CircuitLab The load consists of a resistor and an inductor ...
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### Circuit completes whether base current applied or not - transistor

My fourth electronics project ever. The most challenging yet. I've wired up this project (Project 4 - Short Circuits project kit Jaycar Electronics). After much research, it doesn't do what I ...
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### Is this measurement of a cricuit's output impedance valid?

The following circuit is a simple voltage regulator. The Vout is maintained at -1V, however the opamp in the circuit has a non-zero output impedance. This is represented by the resistor R1. ...
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### Power at the differential output

I was measuring the voltage at the intermediate frequency output of this tuner http://superkuh.com/gnuradio/R820T_datasheet-Non_R-20111130_unlocked.pdf using the oscilloscope. The tuner has a ...
299 views

### What does impedance control on a PCB mean [closed]

I understand that when the electrical length is less than 1/10 of the trace length I would have to go in for impedance matching. A PCB impedance is controlled by its stack up. THat is thickness of ...
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### Getting the numerical value of a capacitor's impedance

I understand that the impedance of a capacitor is $\frac{1}{j\omega C}$. For the circuit above, I have $\frac{1}{Z_V} = \frac{1}{Z_{V1}} + \frac{1}{Z_{V2}} + j\omega C_V$ and \\$V_V = \frac{Z_V}{...
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### Input/output impedance of microcontroller

how to calculate the input and out put impedance for a micro controller , for the purpose of modeling in LT spice , for example RX610 family from Renesas For example the lumped characteristics can ...
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### Calculating Thevenin impedance

This is the circuit I'm given: And after disabling all of the sources, I'm now trying to calculate the equivalent impedance (which would be the Thevenin impedance): But I'm stumped on how to ...
55 views

### Impedance matching photon detector with multiple TTL counting devices

For my scientific work I wish to register signals coming from a photon detector which generates 50 Ohm TTL signals: The expected count rate will never exceed 4 MHz. The devices that need to record ...