Questions tagged [impedance]

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

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Understanding Impedence [closed]

I'm a Computer Programmer and learning Electronics , It has been difficult for me to understand concept of Impedance still , Is there any good Article or Lecture serious which help to understand from ...
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Power consumption on LPDDR4 command bus - impedance options

I'm trying to solicit and opinion on the use of the 60 ohm transmitter/transmission line/ODT for the command bus of an LPDDR4 bus would be better than 40 ohm target impedance. The system uses an ...
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1answer
28 views

RCL circuit sum

Just need help in the daigram of this sum. Can't understand the daigram.will a common resistance be shared between capacitor and inductor or is there 2 resistor and 1 capacitor and inductor with ...
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3answers
185 views

Wien Bridge Oscillator: Why does equating the real part to 0 give the gain equation?

I am learning about Wien bridge oscillators. Following Experiment No. 9: WIEN BRIDGE OSCILLATOR USING OPAMP, they use the following schematic: They then arrive at the following equation half-way down ...
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2answers
36 views

How do I incorporate output and input impedances connected to my circuit?

I'm designing a TTL to VGA DAC for a vintage PC, and I'm confused about the significance of the output and input impedances of my video card and monitor, respectively. The VGA spec states 75 ohms at ...
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5answers
574 views

Parallel resistors deviation

I am building an audio crossover with time alignment based on Douglas Self's design. I desided to make an algorithm to calculate best resistor pair. The first part is easy: Make a list of all ...
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0answers
25 views

Is there a typical “Active Directivity” for LDMOS components?

Active Directivity is a measure of how much an amplifier's source match potentially affects its output impedance, or its load match affects its input impedance. High active directivity is a good thing....
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39 views

How do I calculate the terminal-to-terminal resistance and capacitance from an impedance matrix?

If I have a circuit with \$N\$ ports (and therefore \$2N\$ terminals), how can I calculate the terminal-to-terminal resistance and capacitance from a given impedance matrix \$Z\$? We can assume a ...
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2answers
76 views

Input impedance of the op-amp inverting amplifier [closed]

I have a lab exercise with inverting opamp (gain = 10, R1 = 1k, R2 = 10k). The subject of the lab is to measure input impedance of such amplifier by adding 1k resistor in series to the input and drive ...
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4answers
868 views

Definition of RLC resonance frequency

I have found that a commonly mentioned definition for the resonance frequency in an RLC circuit is defined as the condition where the capacitive and inductive reactances cancel each other, resulting ...
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1answer
71 views

How to calculate input impedance for this simple circuit?

I'd like to calculate the input impedance of the following circuit, assuming that Q1 is "active". I know that the impedance of the voltage divider is \$\frac{R_1R_2}{R_1+R_2}\$ and the ...
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2answers
74 views

What is an op-amp's differential input impedance?

I've heard of differential voltages, but the concept of a differential impedance is new to me. Suppose we are trying to calculate/derive the differential input impedance of the following difference ...
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0answers
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Is it beneficial to use a taper for the feed input of a PCB antenna?

What is your opinion on using a taper for the feed input of a PCB antenna? Say the feed is 2mm wide and the transmission line is 0.45 mm. Would a taper just cause more impedance mismatch? Or would it ...
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1answer
51 views

Motor impedance too high at 20kHz

I have an H-bridge I am driving with an Arduino Mega. The motors I am driving are fairly large, steady state 48 watts, maximum 300 watts. I am driving them at 16 volts and a switching frequency to ...
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3answers
100 views

Why are common mode chokes with 90 ohm @ 100 MHz recommended for USB 2.0 Hi-Speed data lines?

When one looks at common mode chokes for USB 2.0 applications choke manufacturers always recommend CMC with a common mode impedance of 90 ohms @ 100 MHz. Example How does this relate to USB 2.0 ...
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2answers
58 views

How to find Z impedance if I have only S11 (db) and phase

I need to measure Z line impedance. Using VNA I measured S11 it is -53.8785 dB and phase at this point is 175.6706. Could you explain using these numbers how to find R and jR S11 = (Zx-Z0)/(Zx+z0) = -...
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1answer
46 views

Differential Impedance Matching

Below is a small portion of a schematic which I have seen It mentions that the transmission line will have a differential impedance of 100ohms between them. In case of Single ended it would be 50 ...
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2answers
27 views

How does a Touchstone (s2p) file indicate whether it should pass or block DC?

I'm trying to simulate impedance matches for an LDMOS FET amplifier with Touchstone (s2p) files to simulate the device with "real components" before we build it. I have found that "...
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1answer
54 views

Output impedance of a voltage divider with DC bias

I made a circuit simulation of a 200VAC to 0-2VDC for ADC conversion via voltage divider and DC bias with a third resistor connected to a 3.3V supply. What is the output impedance of the divider and ...
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0answers
37 views

The transient instantaneous power dissipation of an impedance

Suppose we have a resistor of value R in parallel with an inductor of value L with series resistance R. The impedance of the network is $$Z= R\frac{sL+R}{sL+2R}.$$ simulate this circuit – ...
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2answers
63 views

Speaker Line Supervision

I want to design a circuit for 100V loudspeaker line control. I want to periodically check if the line is short circuit or open circuit and receive notifications in case of any short/open circuit. I'...
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1answer
67 views

In practice, does the order of a series RLC-shunt circuit matter?

In simulation I'm finding that the image pictured below works well to optimize a complex impedance match. I know that Z = ZL + ZC + R, so in theory the order shouldn't matter---but in practice, with ...
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0answers
98 views

Why the capacitive divider in this output stage?

I have this output driving stage, reverse engineered from a generic Chinese mist generator: The goal is to drive the piezo transducer with a given frequency (more or less 1.7MHz or 2.4MHz depending ...
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39 views

How to calculate \$Z_1, Z_2\$ and \$Z_3\$ in two-port circuit?

I should calculate \$Z_1, Z_2\$ and \$Z_2\$, where \$a_{11} = 1.8, a_{12} = 2kΩ, a_{21} = 1*10^{-3}S\$ and \$a_{22} = 5/3\$? Also, all impedances are resistive, i.e. resistors. I have no idea how to ...
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1answer
43 views

Complex impedance calculation for resistors and coil

I have this circuit and I need to calculate the total complex impedance. Note: the \$r\$ is internal resistance of the coil so how can we calculate the complex impedance? The coil and the resistance \...
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3answers
262 views

How should I probe when measuring output impedance? Why do I get inconsistent readings?

I am trying to measure the output impedance of a commercial headphone amplifier, but the results seem to change depending on how I probe it. When I plug a 1m cable into the device and the other end ...
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1answer
49 views

Calculate impedance in time and frequency?

I'm characterizing the impedance of a system. To get the impedance I apply a sum of sinusoidal voltage waves that basically looks like noise. I recorded the output current from the system. As you can ...
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1answer
72 views

What is the relationship between the RPM, power, and impedance of an induction motor?

Does an induction motor draw more power at higher RPM? Increasing the frequency of the AC power supply will increase the RPM of the induction motor. However, that should also increase its impedance (...
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1answer
53 views

Impedance matching of an amplifier circuit with a filter at the input and output

I created an amplifier circuit with a filter on the output. I did impedance matching on the input and then did matching on the output as well. From the graphs below, is the circuit more matched? ...
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1answer
83 views

Resonant frequency of RLC circuit

Analysis I'm trying to find the resonant frequency for this circuit simulate this circuit – Schematic created using CircuitLab Writing up the node voltage equation for \$V_o \$ $$\frac{V_o-V_{...
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1answer
46 views

Blocking capacitor causing signal to go low in otherwise working amp/rectifier circuit

I'm making a simple amp > voltage doubler rectifier circuit to drive an lm3916 meter circuit and when simming to choose between JFET, BJT or OpAmp (just for my learning, I'm looking to a Jfet in ...
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39 views

What does resistor value change in a passive audio sum circuit?

I'm looking to build a passive audio sum box to connect two mixer headphone outputs (with output impedances of 10 Ω and unknown) to a single pair of headphones for music performance. I plan to use my ...
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3answers
89 views

What's the correct approach to this RLC circuit problem about RMS voltage?

How are you supposed to determine \$V_{C,RMS}\$ without R, L or C? I drew a phasor diagram and used \$Z=\sqrt{R^2+(X_L-X_C)^2}\$ but am unsure on how to proceed from here as I do not have values of R,...
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4answers
524 views

Do the formulas for capacitive and inductive impedance always hold?

The current through a capacitor is given by \$i_c=C\cdot \frac{dv_c}{dt} \$. Let's say the voltage across the capacitor is a cosine wave. \$v_c=\cos(\omega t) \$. Due to the complex exponential ...
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2answers
112 views

Unexpected ADC behaviour - can anyone help diagnose?

I'm attempting to read an air temp. sensor made by Amphenol (Datasheet). The sensor outputs is pulse density modulated (PDM) and is filtered to DC using a simple LPF as suggested by the manufactorer. ...
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3answers
324 views

Trouble understanding output impedance of common collector

I'm self-studying electronics. I'm currently following "The Art of Electronics" (p. 84, 2.2.5 Emitter follower biasing), helping myself with additional videos and tutorials as I go. I'm ...
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1answer
43 views

How to add remote testpoints to non-multidrop RS422 without causing reflections?

I have a RS422 non-multidrop connection between two connectors on a PCB (CLK+/- and DATA+/-) clocked at 1MHz, and currently routed with adapted edge-coupled microstrips (120Ohm differential impedance)....
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2answers
91 views

Bad Reflection from SMA Board Connector at 4-8 GHz

recently I have tried to design a simple SMA-to-microstrip connector PCB intended for 4-8 GHz. The connectors used are vertical with surface-mounted centerpin (link). The design idea was to simulate ...
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1answer
90 views

Why USB 2.0, USB 3.0, PCI signals must be routed in 85E differential ohm impedance and not 100E impedance?

USB 3.0 and USB 2.0, pci signals, Why its always recommended to route at 85E impedance and not 100E impedance? Below are the signals to be routed at 85E D− (USB 2.0 differential pair) D+ (USB 2.0 ...
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2answers
76 views

Purpose of 100 ohm resistor on guitar pedal output buffer

On the schematic for an Ibanez "Tube Screamer" there is a 100 ohm resistor in series with the output emitter follower: The output impedance of this pedal is 1.2K: It looks like RB has a ...
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1answer
38 views

RF via impedance calculation with NFP removal

I'm trying to match the impedance of a RF via from bottom layer to top layer in a 6-layer PCB design. GNSS signal. Unused pad (NFP) removal activated. The selected via size is 0.9mm pad and 0.5mm ...
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1answer
117 views

Damping output filter of buck converter?

Does anybody know if we need to damp the output filter of a buck converter? I came across this paper Passive Power Filters written by R. Künzi. In this paper he suggested an approach to damp the LC ...
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1answer
49 views

Does a simple wire antenna need a 50 ohm transmission line? [duplicate]

I am trying to make a LoRa board with an RFM95W module. Using the calculator shown in the image below, I designed a 50 ohm impedance transmission line. I added options for both a monopole copper wire ...
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0answers
71 views

Output impedance of JFET source follower with constant-current biasing

I try to study the output impedance of a JFET amplifier biased by a current source, but I can't do it. I know how to determine the output impedance of a JFET amplifier polarized by a voltage divider, ...
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0answers
19 views

Feed-through termination to vary bandwidth and signal power

I'm currently facing an interesting problem regarding RC low-pass filters. In my experimental setup, I have a reverse-biased photodetector (DET01CFC from Thorlabs). To amplify this signal, I make use ...
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2answers
313 views

Transmission lines with same impedance but different dimensions

Suppose we connect two transmission lines with characteristic impedances \$Z_1\$ and \$Z_2\$. The reflection coefficient looking into the transmission line with impedance \$Z_2\$ is $$ \Gamma=\frac{...
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1answer
71 views

Impedance matching L Network

I‘m trying to understand exactly what an L-section Network does. I understand it tries to eliminate the imaginary part of the impedance and match the real part. However I do not understand what ...
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1answer
74 views

Impedance in LTspice and current plotting

I wanted to try a test simulation on LTSpice to understand few things. I have a RLC parallel circuit and I wanted to see how the impedance varies according to each one of the components (very easy but ...
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0answers
30 views

Photodetector and low noise amplifier acting as low pass filter

I need some basic advice for impedance matching: I have a photodetector (Det01CFC from Thorlabs, https://www.thorlabs.com/drawings/275cb418cdc2cf1f-A2E46103-D9C0-3581-4553E3D3CA93AD83/DET01CFC-Manual....
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1answer
59 views

PCB antenna track and SMA connector controlled impedance

I designed a pcb for GSM module, using all the specifications given by the manufacturer, to have a controlled impedance. But there is a small detail that escapes me and that is not documented. When ...

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