Questions tagged [input-impedance]
The input-impedance tag has no summary.
254 questions
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High speed signals and control impedance traces
What exactly is the definition of a high speed signal? Would you consider a signal of 1 MHz a high frequency signal? Or does it depend on the rise and fall time (the edges are what create harmonics)?
...
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4
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Finding input resistance
I am trying to find the input resistance for the following circuit, but struggling to know where to even start:
From general method of connecting a known voltage source to find the input current does ...
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215
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Input impedance common-mode of an Op-amp
In an op-amp (OPA838) the input impedance common-mode is as follows:
What is the range for the input impedance?
I want to interpret this: (35 || 1 MΩ || pF)
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Input impedance for MAX41470 receiver IC
Datasheet
The Smith chart on page 13 suggests complex input impedance:
While at page 32 it clearly states:
The LNA is a broadband gain block that increases the amplitude of a signal received from ...
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Photodiode amplifier - OpAmp current noise contribution calculation
A common noise model of a Photodiode amplifier is the following:
(for example in https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/14/noise11_2D00_Photodiode_2D00_Noise-1....
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Equivalent Resistance of a Differential Source Seen by Differential ADC
In the following diagram, I would like to know how to find out equivalent resistance seen from points A and B (input terminals of a differential ADC)?
I'm trying to determine if the source signal has ...
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1
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OPA - How to calculate the input Impedance
I would like to ask if anyone could explain to me how to calculate the Input Impedance of a given circuit, if the OPA used is an Ideal one.
The task is also to create a simplified schematic of this ...
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Input impedance of linear blocks
If the input impedance of a linear block A is Rin1 and that of block B is Rin2 while the other terminal is grounded as shown, is there a way to find out Rin3 when A and B are in series?
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Diode SPICE model for the HSMS-2860 in CST schematic
Trying to create diode in CST schematic but getting this error.
Use same values and import it in CST as .lib file (notepad file names as .lib). Transmission lines used for impedance matching.
...
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Why is diagram b the simplified diagram for this multi stage amplifier?
The following is from the book RF MICROELECTRONICS Page 56.
Determine the noise figure of the circuit shown in Fig. 2.53(a). Neglect transistor capacitances, flicker noise, channel-length modulation, ...
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Can a low-impedance analog input cause a sensor output to oscillate, overheat, or fail?
I have a dual output sensor connected to two analog inputs on a controller.
The main output of the sensor works from 0.5 to 4.5 V DC and the other output is inverted such that it works from 4.5 to 0.5
...
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How would I use a Smith Chart and L-network to set input admittance of a circuit network?
I'm doing the practice problem pictured below:
Find d1 and d2 with:
$$Z_o = 50 \Omega \hspace{5mm} Z_L = 100 \Omega \hspace{5mm} f=10GHz$$
So that:
$$Y_{in}=20\angle30^o\hspace{1mm}mS$$
I summed up ...
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Derivation of the AC small-signal circuit and the canonical form of a DC-DC buck converter
I'm new to this forum and hope you can help me. I am in the process of designing an input filter for a DC-DC step-down converter 12V-5V/1A (Pic.1).
I am trying to determine the transfer function and ...
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Why does the author assume \$R_{in} = 1/ g_m \$ for this this circuit?
The following circuit is from Chapter 13 of Analog Design Essentials, page 1324, written by Willy Sansen.
Calculate \$R_{in}\$ for this circuit.
The author thinks \$R_{in} = 1 / g_m\$
However,
$$
-...
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Connecting an op-amp to a second-stage amplifier: loading effect considerations
I designed an amplifier with an OPA838 as follows:
First scenario: I want to connect the OPA838 to a next stage voltage LNA (Low Noise Amplifier).
What components or circuit should I add to my output ...
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118
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Watching an open-collector input without disturbing it
I'm trying to control an opto-isolator (actually a photorelay such as a TLP354x but it doesn't really matter here).
The problem lie in an external device (black magic box) which is also controlled by ...
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The effect of input and output impedance
This picture shows the classical feedback system and this assumption about this system.
"the input impedances of both the amplifier and the feedback network are
infinite and their output ...
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2
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120
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LM3900: different input impedances in symmetric pins?
Referring to the LM3900 "Quadruple Norton Operational Amplifiers" datasheet, consider the schematic of each single amplifier at page 1.
simulate this circuit – Schematic created using ...
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May I safely apply negative voltage to PIC's analog input?
For example I'd like to apply AC voltage ~3V. Could I not detect, but simply connect to MCU? I'd measure positive side as regular ADC, but I simply do not want negative side of amplitude to damage it. ...
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How can we calculate complex impedance when there is capacitor in the transistor circuit?
The following is from the book book Design of Analog CMOS Integrated Circuit, Page 187.
With the aid of Miller’s approximation, we have from Figure
$$Z_{in} = \frac{1} {\Biggr[C_{GS} + (1 + g_m R_D) ...
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Calculate the input resistance of the circuit with Miller's Theorem
The following is from the book Design of Analog CMOS Integrated Circuit, Page 176.
Calculate the input resistance of the circuit with Miller's Theorem.
In order to calculate the gain.
The current \$...
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Oscilloscope input clippers
The analog front end of an oscilloscope begins with an attenuation stage. Mostly they use two attenuation stages, like 1/1 and 1/50.
From: Rigol Homebrew Wiki - schematics page
The image above ...
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Why is the standard procedure for obtaining an equivalent circuit for bilateral amplifiers valid?
(Note that this question is related to this one, though this question represents my having somewhat better understood the "modification" alluded to in the linked question and wanting to ...
- 1,259
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212
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Differential input impedance derivation
I have been looking into differential amplifier circuits, differential input impedance, and common-mode input impedance.
Everywhere I go (such as here or here), I see this as the solution for ...
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2
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238
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Input/output resistance for an accelerometer/Wheatstone bridge
I am looking at the MS 3028 Piezoresistive Accelerometer.
This is the internal schematic of the component, as a Wheatstone bridge, which per my understanding means it's a quarter bridge with other ...
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110
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Output-Z (electret) higher than Input-Z (preamp)
What happens if an electret microphone capsule (JFET in catridge) is connected to a preamp with considerably lower input impedance than the capsule's output impedance itself?
ECM output Z: 2.2K
Preamp ...
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928
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NE5532 as a Guitar Pedal Buffer
I’ve been trying to better understand the NE5532 and wanted to try designing some circuits with it. I wanted to do a dual-supply non-inverting guitar pedal buffer, but I’m concerned about the input ...
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222
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Complex Input Impedance of Autotransformer with Complex Load
I am interested in the input impedance Zin of an autotransformer with coupling k and complex load Z1 as shown in the picture. Does anyone know how this can be calculated?
This is what I tried so far. ...
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197
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RF amplifier class A
I have simulated a class A RF amplifier. When I simulated the output impedance, it is around 50 Ω for the frequency range that is of interest (50 kHz to 100 MHz), now at the input impedance is around ...
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265
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What is the standard form for writing the second order transfer function for Input impedance?
When writing the transfer function for a system, the Characteristic equation in the denominator which carries information about the poles of the system is equated with the standard second order ...
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What is the resistance of this equivalent-circuit?
In order to cofigure an ADC, I need to know the input resistance to the ADC Pin of a uC, designated as R_source in the following equivalent circuit:
From ...
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Computing input resistance of two common-base configurations
When computing the input resistance of this common base configuration, the collector current \$I_C\$ is approximated as equal to the emitter current \$I_E\$:
simulate this circuit – Schematic ...
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115
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Does high pin impedance affect the need for resistors?
I'm designing a brushless motor controller as a hobby project. I'm using the MP6538 gate driver (datasheet here: 1), and I have some questions about pin impedance and whether or not resistors are ...
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Can I pull down with 5V logic a not-level shifted (which is at 2.8V logic pulled-up) input? How to pull it up to 2.8V again, with no level-shifters?
I have a Distance sensor which has an enable pin (XSHUT pin in the diagram) which is pulled high in its own PCB module at 2.8V, to enable it to work. My Attiny85 MCU, which controls the sensor, is at ...
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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)...
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Transistor Re Model Input/Output Analysis
I have been trying to derive Av , Ai , Zi , Zo from a two port system model of a transistor. I know that the input voltage must be the voltage at the base to ground, and the output is from collector ...
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91
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Weired result of Ltspice Zin measurement, Phase shift of -104°
I am trying to measure the input impedance of this amplifier to design a matching network for it. But the input impedance I get has a phase of -104° at the frequency of interest. I thought that Phase ...
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Input resistance of an inverter op-amp circuit
I need to find the input resistance of this circuit. There are two parts of this exercise:
The first one is to find the input resistance of the circuit without the capacitor.
The second is to the ...
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2
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228
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Input resistance of an op-amp circuit
I need to find the input resistance of this circuit. There are two parts of this exercise:
The first one is to find the input resistance of the circuit without the capacitor.
The second is to the ...
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What is the difference between these two input impedance equations?
I'm currently solving some university E&M homework problems and to solve input impedance, we were given this formula (from Fundamentals of Applied Electromagnetics 6th Ed):
But when I browse ...
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813
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How to buffer (high input impedance required) a differential signal
I'm wanting a to increase the input impedance to a differential ADC. The ADC spec states that it can't handle a negative voltage lower than -100mV the ADC's supply can handle ~5V (this is a ATtiny1617)...
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249
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How can I get the input impedance of this multistage amplifier?
I was trying to figure out the input impedance of this multistage amplifier.
The input impedance of the other stages can be simplified to \$R_{i2}\$.
I tried to replace T1 with the hirbid model but ...
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275
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Why do LDMOS RF power transistors have a low real resistance?
I've been looking through datasheets for RF LDMOS amplifiers for use in an RF power amplifier. They typically have an input impedance that has some small real part of the resistance (<10 Ω) with a ...
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Impedance of antenna and noise propagation
I would like to better understand how noise is radiated.
Suppose the circuit under study is a circuit with a DC/DC converter (source of noise) and an analog circuit (receiver) which is very sensible ...
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66
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Input impedance when an opto-isolator is in series
My circuit is detecting 24Vac/dc signals with an opto isolator at the input. HCPL354 is the opto isolator and I am adding 4.4Kohms resistance in series to limit the current. When I make the datasheet ...
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3
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296
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Measuring variable impedance
I was wondering how to design a measurement system that's able to correctly measure a load impedance that can vary over time and can possibly have very low as well as very high values (see figure ...
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When should an unmatched antenna be measured with a cable length in even multiples of a half-wavelength?
A few years ago someone told me that if you use a cable which has a length of an even half-wavelength multiple for the frequency being tested, then the impedance measured at the end of that cable will ...
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1k
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How to lower input resistance of buffer (unity-gain) op-amp?
A practical op-amp connected in a unity gain configuration will have a very high input resistance (mega-ohms or higher). How can I add an external resistor to modify the input resistance to the kilo-...
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65
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ADC input impedance - DC682a with sensor
I need to read sensor position with 16 bit resolution, with this spec:
I currently have in hand the DC682A ADC, but Im not sure if I can use it from datasheet LTC1859: "The input impedance is ...
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