# Questions tagged [input-impedance]

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### 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 ...
43 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 ...
33 views

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### 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 ...
402 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 ...
47 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 ...
131 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 ...
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.
229 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 ...
163 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 ...
51 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 ...
169 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 ...
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### 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) ...
282 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. ...
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### 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 ...
121 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 ...
262 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'...
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### 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 ...
284 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 ...
172 views

### Achieving high-input impedance for a voltmeter front-end

So, I'm starting on the front-end for my digital project, figured out the ratios (100kΩ, 900kΩ, 9MΩ for ÷10 and ÷100), tolerances (0.05% - 0.1%) and temperature coefficients (< 50ppm/°C might work) ...
1k views

### When talking about input and output impedances, what are we comparing them to?

Let's consider a theoretical highpass filter: simulate this circuit – Schematic created using CircuitLab I'm trying to show that the worst-case input and output impedance is R but the whole ...
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### How to test the input impedance of a Microphone Preamp?

How would someone test the input impedance of a microphone preamp? I have all the necessary equipment i.e. oscilloscope and multi-meters but I'm struggling to find information on the topic.
358 views

### Op-amp ideal characteristics

In a textbook, it says that the ideal op-amp should exhibit following electrical characteristics and one of them is - ** Infinite input resistance (R) so that almost any signal source can drive ...
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### Is the dynamic input resistance zero for constant voltages?

This might sound a stupid question but I'm confused with the following excerpt: If Vbe is constant 0.7V which means ΔVbe is zero, does that mean the dynamic resistance is zero? I think I have ...
580 views

### multimeter input impedance calculation discrepancies

To measure the input impedance of a multimeter, I have built a voltage divider circuit with equal resistances R1 and R2 and measured the voltage across one of them using the multimeter. Considering ...
749 views

### Input impedance of instrumentation amplifier circuit

I am trying to understand the input impedance of this circuit, which is a part of the schematic of this project. simulate this circuit – Schematic created using CircuitLab The circuit ...