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# Questions tagged [impedance]

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

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56 views

### What is the resonant frequency?

I know the formula of resonance frequency for both series and parallel circuits. But when we have a circuit that is shown in the image below where the RESISTOR and INDUCTOR are in parallel and their ...
228 views

### CAN-Bus: Wire Impedance vs Terminal Resistor

I'm seeing several pre-fabricated "CAN-Bus" cables with (2) DB9, 120 ohm terminal resistor connections, while the cable's impedance is 100 ohms. A. What is the purpose for this mismatch? B. ...
63 views

### USB-C board layout question

I have a board design that uses an Amphenol rugged USB-C socket to feed a Microchip USB5744 USB3 hub. When laying out the tracks, it struck me that the 'unused' Superspeed inputs are like stubs on the ...
98 views

### Input impedance of a round straight copper antenna

I got some help from a discussion of yesterday about network impedance matching for transferring data between antennas (Basic RF signal amplifier). The discussion was about that the current and the ...
1 vote
51 views

### Impedance reflection in making a simple current source

I am making a constant current source using the transistor. I am a bit confused regarding the biasing of the transistor. I have seen in many places that when we are setting the biasing of the ...
866 views

### Value of a ferrite bead in PHYs

I have seen a couple of ethernet PHYs whose manufacturer datasheet recommends placing a ferrite bead on the power supply input of the PHY device whose value is, "Generally, a 100-220Ω (at 100 MHz)...
1 vote
53 views

### Common Emitter small signal model for high frequencies simplification

While trying to calculate the high frequency pole frequency corner of the common emitter amplifier I came across the following small signal model (found here in page 332) The small signal equivalent ...
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### Frequency Range VI(Labview)

I tried to understand what "Frequency range vi" consists. But I didn't understand. From Reference Article(doi:10.15199/48.2021.11.10): No.1 shows the block diagrams of fixed-point data ...
63 views

### PCIe "RefClk" impedance requirements?

I'm designing a very heavy impedance-requiremented PCB, with PCIe v2. I know TX and RX diffpairs have strict differential ...
282 views

### Impedance-critical diff-pair routing

I need to route PCIe RX and TX diffpairs: I can't change the bottom connector (fits into M.2 KeyE socket), neither the top (M.2 KeyM socket). Normally, how shall I wire these diffpairs? It seems I ...
33 views

### Differential impedance calculation - which way to go width vs spacing?

In USB2.0 specification, there is a requirement of desigining its data traces to be around 90Ohms +/- 15%. Using this calculator, based on my earlier question I'll need to make sure to approach 90Ohms ...
511 views

### Which impedance matters?

In USB2.0 specification, there is a requirement of desigining its data traces to be around 90Ohms +/- 15%. Using this calculator, with these below data: I got these results: Now, question is, which ...
19 views

### Arc-shape frequency dependence of phase angle in bioimpedance spectroscopy

I have concerned myself with bioimpedance spectroscopy (BIS) from a medical standpoint for some time now, however there is one concept evading my grasp until now: When measuring complex impedance of ...
190 views

### Capacitance for which the ratio of the input and output voltage is independent from the frequency

I have the following circuit with resistors and capacitors in parallel (see Picture 1): I have to determine the capacitance $C_1$ in such way that $\frac{u_e}{u_a} = 1 + \frac{Z_1}{Z_2}$ is ...
76 views

### Total impedance in a circuit

To determine the current I have to calculate the total impedance, here named $Z_{Ges}$, in the circuit which can be seen in the first picture. First I summed $R_1$, $C$ and $R_2$ as a ...
854 views

### Impedance matching on RF PCB

I have two questions about a power amplifier board, see picture. The output of the amplifier has irregular copper traces with different lengths to the output SMA, which I marked (1). Doesn't this ...
45 views

### New ESP32-D0WD-V3 based board has WiFi issues in transmit; receive is OK

I have a custom board with the above chip, and it all works except for the WiFi transmit functionality. I can receive fine with -60 RSSI from my AP 50 meters away, and I receive all my neighbours' ...
114 views

### If the impedance of two coils is measured to be identical at 250.0 kHz, is it safe to assume identical impedance across the spectrum?

This question pertains to matching two air-gap inductors for use in resonant coupling. Alternative solutions are welcomed and appreciated. The two coils shall be comprised of identical wire. The two ...
1 vote
90 views

### Output impedance of small-signal model

When I calculate the output impedance (Rout) of this small signal model, do I have to short circuit between 2 ends of the blue wire or black wire?
82 views

### Band-pass RC filter design understanding

SO i came across an exercise question in a book Design a two-stage “bandpass” RC ﬁlter, in which the ﬁrst stage is highpass with a breakpoint of 100 Hz, and the second stage is lowpass with a ...
76 views

### How to find driving point impedance of non-inverting op-amp circuit

I have this circuit: And I am asked to find the driving point impedance. I know that a driving-point impedance relates the voltage and current at a pair of terminals. The formula for the driving-...
88 views

### How to derive transistor input impedance?

Given the following circuit, When Ro is not infinite, from the book, ZB is given as, However, when it's infinite, the input impedance is easily obtained as the parallel combination of RB and β(re+RE)...
226 views

113 views

### Crystal resonator characterization in frequency and time domain

I want to measure a 32.768 kHz crystal resonator (not oscillator) in the frequency and the time domain using a ZURICH HF2LI instrument, which is a network analyzer and oscilloscope in one unit. The ...
77 views

### Output impedance of the circuit

I would like to know what the output impedance of this circuit is (the impedance seen by the node output).
158 views

### Frequency response of LC filter with resistance in parallel with the capacitor

The following is the diagram of interest: The impedance of the filter is: $$Z_o=\frac{R_f L_f s}{R_f L_f C_f s^2+L_f s+R_f}$$ and the bode plot with all different components and the total impedance ...
66 views

### Input impedance of an electronic load

I would like to simulate a TVS with an electronic load working in constant voltage. I could add some resistor in serie with the electronic load to simulate the dynamic resistor of the TVS. ...