Questions tagged [input-impedance]
The input-impedance tag has no usage guidance.
140
questions
0
votes
1answer
52 views
Measurement of s11 with reduced power on NanoVNA
I am developing a 10.7 MHz IF amplifier for a radio receiver. In order to match the input to the output of the driving mixer stage (330 ohm) I need to measure the input impedance.
I did the ...
0
votes
1answer
59 views
Modelling differential amplifier input circuit
I'm trying to understand the behavior of a filter connected between a mixer and fully-differential amplifier. Here are the relevant portions of the schematic. The first part is the mixer output
5VF ...
0
votes
0answers
36 views
Phase and Gain of transimpedance amplifier and effect of input impedance
I am new to hardware design. I am designing measurement circuit for Impedance Spectroscopy of electrochemistry cell. I need to measure the current coming from electrodes which have range from few ...
0
votes
2answers
46 views
What does a simple passive circuit to simulate an impedance mismatch look like?
I am trying to learn some of the basics of circuit design. One thing I am curious to make a filter/schematic of is what happens when a voltage source hits an impedance mismatch.
eg. A high impedance ...
0
votes
2answers
75 views
Sziklai pair and Darlington pair input impedence
If i remember correctly the input impedence of a BJT is r_pi=Vt/Ibq.
I've read that using those two configurations I get a much higher input impedence. Can someone please tell me why? Maybe some ...
0
votes
2answers
97 views
What makes a input GPIO pin so sensitive?
I know that an input pin has a high impedance, but how a high impedance makes such pin be so sensitive?
According to https://forum.arduino.cc/index.php?topic=454553.0 -- #4 mentioned
If the input ...
3
votes
2answers
61 views
How to integrate current signal to be able to measure it with 50 ohm input impedance of ADC
Preliminaries
I am using a photomultiplier tube (PMT) in order to amplify scintillator's light signals. Some of the studied scintillators have long decay time and poor light yield. That makes these ...
0
votes
2answers
64 views
Why is the input impedance of an emitter follower defined as \$\Delta V_{B}/\Delta I_{B}\$, as opposed to \$V_{B}/I_{B}\$?
In The Art of Electronics, chapter \$2\$:Transistors, page \$65\$, the author defined the input impedance \$r_{in}\$ of the emitter follower below
as \$r_{in}=\Delta V_{B}/\Delta I_{B}\$. Why did ...
0
votes
0answers
43 views
Input and Output Impedances of Differential Amplifier
I have this circuit that is used to convert an incoming analog differential input signal to a single ended signal. The differential input is connected at IN+, IN- and the output is taken from OUT.
I ...
0
votes
1answer
88 views
FPGA input capacitance
I want to estimate power consumption of a battery powered digital circuit that has a CPLD (Lattice LCMXO2-256HC). It receives 64 MHz signal into LVDS input and 10 MHz, 2.5V into a schmitt trigger ...
1
vote
1answer
76 views
Why does the common collector specifically have a high input impedance?
When looking at a chart comparing different BJT amplifiers, the common collector/emitter/base, it is usually said that the common collector has a high input impedance, therefore it is suitable for use ...
0
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0answers
35 views
Input impedance of transmission lines
I want to calculate the input impedance of this circuit, could you please check my calculations if it is correct? Z is the characteristic impedances and theta is the electrical length of the TL.
$$
...
0
votes
1answer
173 views
How can I interface with arduino mega2560 to detect the presence of a 48 V without pulling down the voltage by more than 0.1 V
How can I interface with a microcontroller to detect presence of a 48 V supply with a source impedance of 10 kΩ without pulling down the voltage by more than 0.1 V?
I need to step down the output ...
0
votes
3answers
125 views
Op-amp input impedance
I was reading the following tutorial from Analog Devices:
https://www.analog.com/media/en/training-seminars/tutorials/MT-040.pdf
They include the following image and state:
In most op amp ...
0
votes
3answers
82 views
How to match a power amplifier and a loudspeaker array?
I am trying to use a power amplifier that is available to me to actuate an array of loudspeakers. The array has a total number of 30 loudspeakers (ways of connection can vary).
And I would like to ...
1
vote
3answers
122 views
How to find input impedance of this OPAMP circuit?
Assume OPAMP to be ideal with infinite gain (a) and infinite input impedance
I am clearly able to see that the input impedance of this circuit is R1 (correct me if I am wrong) but I am unable too ...
1
vote
2answers
80 views
maximum power transfer explanation
Please provide an intuitive explanation of maximum power transfer.
This is a conceptual question therefore I want to ask with an example. I'm wondering in which cases impedance matching is used.
For ...
0
votes
4answers
291 views
Input and Output impedances of Current and Voltage Amplifiers
I read that Voltage Amplifier have high input impedance and low output impedance, and Current Amplifier have low input impedance and high output impedance. If this is true what is reason for this as I ...
14
votes
3answers
2k views
Why are oscilloscope input impedances so low?
My question is two-fold:
Where does the input impedance come from?
I'm wondering where the input impedance of your average multimeter or oscilloscope comes from? Is it just the input impedance to ...
1
vote
1answer
206 views
Input impedance of differential amplifier
Can someone please explain to me, how I should look at the input impedance of the opamps, seen through the voltage \$V_1 V_2\$?
I have two questions on the differential amplifier:
Why doesn't the ...
1
vote
2answers
55 views
Impedance frequency response for a DC motor
Consider the following impedance frequency response for a DC motor :
Its equivalent circuit is :
Clearly, from the response, there exists a capacitor, inductor, and resistor, but my problem is how ...
-2
votes
1answer
65 views
How do I find input impedance here?
I'm not too sure how to go about doing this. Added what I did so far but I don't know where I messed up.
0
votes
2answers
112 views
Input Bias Compensation Resistor Calculation for an Integrator
I have been reading the following tech note from Analog Devices that discusses designing an op amp circuit to compensate for the input bias current: https://www.analog.com/media/en/training-seminars/...
3
votes
1answer
210 views
Impedance calculation from voltage and current (exponential) waveforms
If we want to find the impedance across two terminals (a port) at a frequency \$\omega_0\$ using the voltage waveform across \$v(t)\$) and current through (\$i(t)\$) the terminal, general intuition is ...
10
votes
2answers
566 views
How are such low op-amp input currents possible?
I understand that op-amps have low input currents; that's one of their defining characteristics. But looking at the datasheet for the LMC6001 (amusingly called an "Ultra, Ultra-Low Input Current ...
4
votes
3answers
1k views
Strange opamp's output impedance in spice
I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532"
I want to measure the input and the output impedance. I expected an output ...
0
votes
2answers
47 views
Change range of data acquisition system
I have a DAQ with many inputs that can measure within +-10 V, and I want to go up to +-30 V.
Using a resistor voltage divider could be an option, but this lowers the input impedance. I would prefer ...
0
votes
1answer
38 views
Confusion between Input/Ouput Impedance and Thévenin's theorem
I'm bit confused about what Input Impedance or Output Impedance is. I tried to read Wikipedia's page (https://en.wikipedia.org/wiki/Input_impedance) but I find it hard to follow.
Is the Input ...
2
votes
2answers
259 views
Emitter follower and input impedance
I'm designing an active bandpass filter (using only BJTs, voltage sources, resistors and capacitors) with the following properties:
Corner frequencies \$8 ~ \text{kHz}\$ and \$800 ~ \text{kHz}\$ (...
0
votes
0answers
104 views
Correct way to calibrate SDR RX into a measuring receiver
While playing with my SDR (Software Defined Radio) Board, I was interested in performing a TX output power table at different center frequencies and TX antenna gains.
However, unfortunately, I do ...
0
votes
1answer
59 views
Calculate input resistance of power amplifier
how can I calculate the input resistance of this circuit?
Thank you!
0
votes
2answers
124 views
Input impedance of circuit
Given current gain (hfe = 100), internal resistance (hie = 2000), reverse voltage gain and output resistance (hre = hoe = 0), compute input impedance for the following circuit.
The problem is that it ...
0
votes
2answers
255 views
Is static negative resistance practically available?
I learned that negative resistance (NR) could be simulated by involving active devices like op-amps and others. I'm interested in the static/absolute NR rather than the differential NR.
My question is ...
0
votes
2answers
165 views
Finding input impedance of the circuit
I'm having difficulties finding complex impedance of the following circuit:
What I did first is find the impedance of \$C\$ and \$R\$ in parallel, which is:
$$\underline{Z}_{CR}=\frac{R}{1+j\omega CR}...
0
votes
1answer
107 views
Input impedance of common-collector configuration
We have been asked to find the input impedance of the given circuit (above)
I've done the small signal representation of the circuit which is as follows
The question is :
I tried to solve it i'm ...
-2
votes
1answer
767 views
Input Impedance of a diode connected MOSFET
I was trying to derive the small-signal input impedance of a diode-connected MOSFET (figure included), and came up with this expression.
Is my method correct? I have been reading about methods of ...
1
vote
1answer
88 views
What does it mean if input impedance given as a current regulator?
This SSR relay has an input impedance given in its datasheet as:
It says "Nominal Input Impedance is a current regulator". At 5V 16mA.
But how can I model this type of input impedance? I will use ...
-1
votes
1answer
155 views
Removing the imaginary part of input impedance of a Monopole in HFSS
I am building a Monopole in HFSS for my project. Its structure is shown here :
The input impedance at the desired frequency is :
Now i need to eliminate the imaginary part , so that the voltage and ...
1
vote
4answers
168 views
What is the Gain, Input and Output Impedence in this circuit?
So I'm trying to know what the input, output impedence and gain is in this circuit
To begin, I'm kind of confused since I don't know if those two resistors at the right are in series or in parallel.
3
votes
3answers
381 views
Transmission Line Effects
My question has to do with the rule of thumb we generally use when dealing with transmission lines.
We say that if the length of the line is 10% or less of the wavelength, we could neglect the ...
0
votes
0answers
206 views
fast voltage follower (from datasheet of LM318) and current of input terminals
I was looking at the datasheet of LM318 and found the op-amp configuration below (first image). I think the voltage at input terminal 2 is V input. But I wasn't able to figure out what V out is going ...
0
votes
0answers
59 views
low impedance as GND and current measurement, applied voltage sharing the same lead
(Image 1 is for the general idea, image2 is for questions 1 and 2, image 3 is for the 3rd question)
In the setup shown below, the tuning fork is driven by an AC voltage source being connected to one ...
-1
votes
1answer
208 views
Input impedance of Op amp calculation
As a part of my project I created an CMOS Op amp and I want to go through all parameters. In Op amps data sheet there are terms like input bias current and input impedance. How this terms are ...
-1
votes
1answer
56 views
Inconsistent DC Input Resistance in Black Box [closed]
How It's Measured
I have a circuit (can be assumed as Black Box) I want to measure the input resistance (R2) at DC. I do the common method of using a signal (V1) with a known source resistance (R1) ...
1
vote
0answers
297 views
high input impedance circuits
Working with circuits to get high input impedance. This is to capture signals while introducing as little interference as possible to the preexisting circuit, to load the source as little as possible. ...
0
votes
1answer
70 views
Ion-selective electrode: high input impedance to measure the voltage
I read that an ion-selective electrode has an high impedance (\$100 \, M\Omega\$) and that it's necessary a high input impedance to measure the electrode voltage.
I'd like to understand the above ...
0
votes
1answer
179 views
calculate input resistance with known adc value
I am fairly new in the electronics world, but I would really like to learn it. The problem I'm facing right now, is that I miss the insight to be able to tackle this specific problem.
I have to ...
4
votes
2answers
343 views
Op-amp input impedance datasheet specification
Some op-amp datasheets specify both the differential and common-mode input impedance:
while others just specify "input resistance":
I've always assumed that if the datasheet only shows one value, it'...
1
vote
2answers
66 views
Determine the input impedances of a circuit
I'm studying a circuit with BJT's and I'm asked to determine the input resistances of the two amplification steps of the circuit. The circuit I'm analyzing is the following one:
To determine the ...
0
votes
2answers
383 views
Shouldn't internal input resistance of a transistor be almost zero?
I am absolute beginner in electronics and the whole transistor thing is not looking very intuitive to me. Suppose this problem, in active region input terminal voltage almost remains constant with ...
