# Questions tagged [impedance]

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

1,508 questions
Filter by
Sorted by
Tagged with
115 views

### Input impedance of an op amp when sharing bias resistor across multiple op amps

This is a theoretical question more than it is a practical one, and perhaps a bit simple, but I cannot find a reliable answer. Let's say you have a simple op amp buffer like the one below: Source: ...
524 views

### What happens on a CAN bus when impedance is too low?

Assuming impedance is matched with proper end resistors: What is the actual problem on a CAN bus with impedance considerably lower than 120 ohm? For example, transmission line and terminations both at ...
• 497
131 views

### Input Impedance of a converter and output impedance of battery

It is said that the output impedance of an EMI filter needs to be largely lower than the input impedance of a converter in order to have no stability issues. From this document written by Christophe ...
• 2,530
1k views

### What is the difference between using a resistor or a capacitor as current limiter?

Sorry if my question is too basic but I really can't get the idea here. I have this circuit here in which 220 VAC is connected to an optocoupler via these two 120 K resistors results 240 K. What is ...
1 vote
31 views

### Determining the impedance and voltage source with lagging currents

I have the following system where I have to determine the impedance Z1. However the current flowing through this impedance flows after the current of 12A and I'm not sure on how to approach this ...
• 105
102 views

### Audio interface to Headphone calculations

Audio interfaces and Headphones publish different set of specifications. From these, what kinds of calculations can we do to assess whether the interface is capable of driving the headphone ...
89 views

### What is the essence of frequency in DC circuits?

While studying equivalent circuit models for lithium-ion battery packs, I came across the topic of Warburg Impedance. A paragraph from my source (Book Page 40 in preview) goes as follows: In the ...
115 views

### Why is the impedance of ferrite beads different if a current source is used?

From this article from Analog Devices: I built this in ngspice with a current source. This is my netlist: ...
• 951
1 vote
53 views

### Why are my lead acid battery impedance results at different frequencies so similar?

I have six UPSes, each with three strings of 34 blocks off GNB Sprinter XP12V3000. These are connected to a BMS, a PowerShield system for each UPS. For the last year, many of these blocks have risen ...
• 186
80 views

### Completed Daisy Seed Guitar Pedal

This thread is a follow up to this one, and hopefully the last one in my series of questions. The context is: I'd like to make a guitar pedal based on an Electrosmith Daisy Seed. Requirements are to ...
• 49
61 views

### Calculating dimentions of impedance-matched pads on PCB in an RF circuit

I am trying to build an RF amplifier based on an existing design. In my first version of PCB I didn't pay attention to solder pads of the RF transistor (BLF6G21) which were quite large on my reference ...
64 views

### Impedance of a real op amp

I am reading the book Operational Amplifiers by Steve Winder. On page 14, it explains input impedance of real op amps: "... there is a large differential input impedance ... ". How exactly ...
• 159
87 views

### How can I build an impedance measurement circuit?

I am a PhD student and completely new to circuit design. I need a compact-sized circuit and prefer not to use an impedance analyzer due to its bulkiness. I am looking to build a circuit capable of ...
69 views

### Why does the resonance peak dampen when an air cored coil is kept on a conducting material?

I was performing an experiment on an air cored coil, when I noticed that the resonance peak of the coil (Real(Z)) in air was sharp, but when kept on an SS316 plate, the peak dampened. When the coil ...
• 95
1 vote
87 views

### Inverting Amplifier for Impedance and Scaling before Electrosmith Daisy Seed

This thread is a follow-up to this one and that one where I asked for solutions to feed a signal from a guitar pedal device rated 10 dBV (9V p2p) and 10 kOhm output impedance, into an Electrosmith ...
• 49
52 views

### Is it possible to bound the characteristic impedance of a connector pin if it's not impedance-controlled?

I'm currently assessing whether I need a feedthrough connector to be impedance controlled since it carries gigabit ethernet, but only after about 6 meters of cable. So I've made a LTSpice model with ...
• 9,726
220 views

### General solution for the impedance of a finite ladder network with different series and parallel impedances

I am trying to find the equivalent impedance of a network that has a structure like this: I have attempted to use MATLAB with the Symbolic Toolbox to find a solution for the equivalent impedance with ...
• 45
58 views

### Strange non-linearity in inductor impedance

Recently I've disassembled, and rewound a 12+12 V 2A transformer as an autotransformer for a test in impedance matching, but it ended not being enough for what I wanted (although it did work). Then I ...
• 761
49 views

### Variable resistor values for a guitar amplifier circuit

This is a continuation from a previous post. Read here if you have further questions. I have decided to makee a simple guitar amplifier with the circuit seen in the attached figure. What maximum value ...
1 vote
50 views

### What impedance should I shoot for speaker circuit?

I would like to build a simple speaker circuit to amplify an audio signal. I plan on using the CDS-40288 speaker by CUI Devices (datasheet). Questions: How will the impedance of the CDS-40288 affect ...
51 views

### Signal Amplitude drop due to TVS diodes

I hope you are fine. I have a question. I have generated a 4Vpp signal with a 5MHz frequency using the following sequence: AD9851 (DDS) → AD8001 (Op Amp) → Ferrite bead (2KΩ) → Microfluidic sensor ...
66 views

### Why is the output impedance of an open-loop amplifier with a loading effect calculated by breaking the loop like this?

I'm a bit confused about how the author calculated the output impedance of the open-loop transconductance amplifier with the loading effect as follows. (All images are taken from of the 6th edition of ...
• 320
1 vote
133 views

### Op-Amp for microelectrodes in PBS conductive solution

I am using micro electrodes in a conductive solution (PBS: Phosphate Buffered Saline) and I would like to be able to measure the voltage with a National Instrument measuring device (PXIe6345). I apply ...
63 views

### Why does my calculation for transmission line reflection and transmission at a load have infinite solutions?

Take a transmission line with some characteristic impedance and insert a load somewhere along the line. What are the transmitted and reflected signals, given an sinusoidal input. Physically this ...
• 343
38 views

### How to determine exact output impedance of the source degeneration using feedback analysis?

How can I get the EXACT output impedance when looking from the drain side of the source degeneration using FEEDBACK ANALYSIS? It can be derived easily using a couple of methods, but I'm having some ...
• 320
999 views

### Infinite output impedance in amplifier, instead of 0?

The question asks: "Exercise 14.5 Assume an ideal op amp and use the summing-point constraint to find an expression for the output current io in the circuit of Figure 14.14. Also find the input ...
94 views

### Why does tan (θ) equals -j in impedance of reactive circuits?

I'm having trouble understanding the maths for impedance. Suppose we have a voltage of $V(t)=V_{0}sin({\omega}t)$ and we plug this into the capacitor equation $I(t)=C\frac{dV(t)}{dt}$. This would ...
• 162
445 views

### Do audio impedance mismatches cause reflection (ie, 8-Ohm output to 20kOhm input) ? Does it matter?

I understand that audio source⇒input impedance mismatches are normal, and this answer provides a good reason as to why. However, having worked with RF more than audio, mismatches cause reflection that ...
• 2,180
282 views

### What does impedance seen from input/output mean?

I am seeing it usually like impedance seen from input/output when we need to match impedances between two circuits. What does it even mean? Does impedance change based on where do you look from?
• 271
34 views

### Impedance measurement using AD 5933

I hope this message finds you well. I am using the AD 5933 evaluation board for impedance measurement, The data sheet says it can measure the impedance up to 10M ohm. I am currently measuring the ...
177 views

### Source impedance-trace impedance - load termination impedance confusion

I drew an experiment PCB to better understand the PCB impedance. And when I look at the impedance at 1 GHz, it can be seen that it is 119 Ω at most points of the trace. Then, I created a source that ...
• 768
665 views

### Why does the voltage double at the end of line in a open transmission line (physical explanation)

I'm seaching a way to explain physically what happens in a wave reflection in a transmission line, if we apply a DC voltage in a open circuit transmission line, the voltage at the doubled. I saw this ...
109 views

### Pi-Filter Simulations Comparison

I am trying to simulate the filter impedances on LTspice. There are two images of the simulation results of the same pi-filter on LTspice and Redexpert. Although I am not sure the parameters are ...
1 vote
148 views

### How can this Clapp JFET oscillate when its gate is tied to ground at the resonance frequency?

How does the circuit below oscillate? It seems to have |gain| < 1 at its oscillation frequency of 2.25 MHz, yet it oscillates there. My analysis: The DC path is through L4 only, allowing a bias ...
• 1,317
59 views

### Non buffered CMOS logic gates working under load when using real components (LTSpice Sim)?

I'm experimenting with CMOS logic gates and have encountered something I am having a hard time understanding. When I make an inverter using ideal components and measure the output, it works exactly as ...
• 165
47 views

### Is a smoothing capacitor only useful when the trace has impedance

Under conditions where maybe a capacitor is used maybe when perhaps there's a high impedance power supply and the source would cause current surges, maybe a subwoofer to a car battery that can't deal ...
• 679
506 views

### How can these passive RLC circuits change a sinusoid's frequency?

Given a sinusoid input of frequency f, an RLC network, no matter how complex, should produce a sinusoidal output of frequency f, with possible attenuation and phase shift. At least that's my ...
• 1,317
63 views

### What requirements of a feedback network are needed to produce oscillation?

I'm trying to understand how to analyze simple oscillators, and would like to know if my conclusions about the required feedback network are correct: The simplest way to build an oscillator is with: ...
• 1,317
89 views

### How to analyze and simplify a voltage divider with a second voltage source?

How do I simplify the circuit below? simulate this circuit – Schematic created using CircuitLab I know that R2 and R3 form a voltage divider, but I can't figure out the input impedance that In ...
• 1,317
1 vote
164 views

### Impedance for a guitar pedal into an Electrosmith Daisy Seed ADC

I'd like to be sure I can feed my guitar pedal signal into my Daisy Seed ADC to then work on it with digital signal processing algorithms. Here is what I know about my problem: It seems guitar pedals ...
• 49
55 views

### Why would changes in the impedance of a transducer affect the voltage displayed on the oscilloscope?

In my setup, a function generator is connected to an amplifier that drives a transducer. The amplifier output is connected to both the transducer and an oscilloscope via a tee connector. I do not ...
68 views

### RC series analysis with H parameters model

I'm writing this just to be sure I understood well the process of analysing a circuit with the $H$ parameters model. In this case, it is a very simple example of application; the circuit I'm ...
97 views

### How to calculate $R_{out}$ in this multi-stage close loop?

The following circuit is from Chapter 13 of Analog Design Essentials written by Willy Sansen. Calculate $R_{out}$ for this circuit. The author thinks L_G = g_{m1} r_{o1} g_{m2} r_{o2} \frac{R_1} ...
• 951
68 views

### How to calculate the output impedance of a gain-boosted biasing circuit [closed]

I've been working on calculating the output impedance $R_{Out}$ ​of the gain-boosted biasing circuit shown in picture, where all transistors are in the saturation region. While I understand the ...
• 31
1k views

### Which is preferred over differential pairs: trombones or sawtooths?

I have been told that trombones are much better to use than sawtooths, even if sawtooths may be prefered in some certians scenarios. Here I have added trombones to the differential pairs. If I had ...
• 1,386
1 vote
92 views

### Is it possible to simulate reflections by designing an RLC transfer function?

Assume that you're knowing the PCB stack and the geometry of the conductor. You're computing the capacitance per mm and inductance per mm and also the total resistance of the conductor. That means you ...
• 1,386
33 views

### LCR meter U1733C - R range mesurement

I have the LCR meter "U1733C" and I am little confused about the "R" scale. As I understand (the manual doesn't say it clear - maybe it is self-evident and I am missing something) ...
• 373
576 views

### Resistance Vs Reactance Definition

I am trying to understand the practical distinction between resistance and reactance. As I understand from all what I read the resistance is responsible for the current flow and the reactance is ...
• 373
82 views

### Difference between characteristic impedance vs complex impedance

Are there any differences between complex impedance of antenna pcb trace vs characteristic impedance of antenna pcb trace. This question rised up because of online pcb trace impedance calculator doesn'...
• 11
1 vote