Questions tagged [small-signal]

A circuit analysis method in which non-linear elements are replaced with linear elements whose parameters are determined by a linear approximation of the non-linear element's characteristic curve near its bias point. The result is an equivalent circuit that is a good approximation of the original circuit for signals small enough that the non-linear elements behave linearly (hence the name "small signal").

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Is the bulk grounded in small AC signal analysis?

This the circuit. The bulk is connected to ground in DC. Is the bulk grounded in small AC signal analysis (Vb = 0)? How about for PMOS? When the bulk of PMOS is connected to VDD, is the bulk grounded ...
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For a degenerated CS amp with current mirror would the small signal model include the current mirror

I am aiming to create an actively loaded degenerated CS amplifier and analyse the small signal performance in relation to maximum signal levels, maximum signal swing, voltage headroom requirements, ...
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Differential output resistance with LTSpice

I have a simple NMOS FET where I would like to plot the differential output resistance at the operating point of Vgs = 1.7V (which is the Vgs voltage for Id=9.4mA) I managed to plot the output ...
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MOSFET small signal model question

Why is vgs = vin - vout as stated in the image? The book has gmvGS wrong as it's supposed to be a current source.
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How to draw the small signal equivalent of this circuit?

I need to convert this circuit into a small signal circuit but I am having a hard time drawing it. I think it is wrong at the FET-transistor connection to the bipolar-transistor.
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If I want to limit the bandwidth of this BJT to 10 kHz, what resistance should I consider when need to calculate the value of capacitor Cf?

My wish is to get the capacitance value by calculating R when I use the hybrid-pi model, so use the formula Cf = 1 / (2 * pi * f * R). I would like to ask if the R value needed to use in the above ...
YY927's user avatar
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Why are capacitors treated as shorts in small signal models?

If I understand correctly, a small signal model (e.g. hybrid pi modal of MOSFETs) is just a linear approximation of a nonlinear circuit centered at the DC bias point. At DC, ideal capacitors act like ...
Mikayla Eckel Cifrese's user avatar
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Minimizing small signal relay bypass pop

Attached is a stripped down version of the circuit. The relay is controlled by a push button going to a microprocessor then powered by a BJT with a flyback diode in parallel. The output of the DSP/etc....
OnlyServeSwill's user avatar
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1 answer
159 views

Circuit Analysis - Diode Small Signal Voltage

I'm struggling with this circuit analysis about a pn-junction diode. I'm given I_D = 1.066 * 10^-7 A when V_D = 0.6V and I_D = 2.2 * 10^-5 A when V_D = 0.8V (all at room temp). My calculated values ...
lemonstella's user avatar
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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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Does signal source of mobile phone, from its 3.5mm headphone jack, act as a current source or as a voltage source?

Even though the audio output of the mobile phone (which we draw through 3.5 mm jack) outputs a signal that's a function of time, at a very short interval of time, this source acts as a dc source of ...
Cinverse's user avatar
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Small Signal Model of Two-Switch Forward - Basso

I've designed a two-switch forward converter, that I would like to create a small signal model for to examine the stability criteria of the converter and then compatibility with the EMI filter... A ...
user397703's user avatar
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Cascaded BJT Amplifier

I found this circuit in here. I know that it's a multi-stage cascaded BJT Amplifier and I know how to calculate it. My question is, what R8 is used for? And If I remove it, is it cause any problem or ...
Jnote's user avatar
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Thevenins equivalent resistance with only dependent sources

What is the Rth of the below circuit Given R=R1=R2=10 ohms and g=10 siemens. Below is my solution.I am getting a value of 0.2 Ohms for Rth.May I know is this correct.
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Finding transconductace Gm=Isc/Vin for a common source MOS amplfier with source degeneration

I am looking to find short circuit current over input voltage to find transconductance Gm for a common source amplifier with source degeneration. To do this, I first shorted the output terminal and ...
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How to give small voltage signal to Arduino?

I have a device which audibly says a specific line, let's say it says "received payment of $5," and the device has a speaker connected. Now I want when it says this line, my Arduino should ...
Shashank Kumar's user avatar
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Calculating frequency response of a RF tuned collector amplifier

I am doing a frequency response analysis for the following RF tuned circuit. I am not sure if I have done the right calculations so please correct me if there is any mistake. The DC equivalent ...
Shubham Agrawal's user avatar
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Theoretical calculation of gate delay

I am currently working on not-gate based ring oscillators and I was wondering if there was a way to theoretically calculate without having to look at the simulation graphs the rise time and fall time ...
KaBe2003's user avatar
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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 ...
13A's user avatar
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Can I do AC analysis of a transistor solely using the input/output impedances provided by the datasheet?

I learned to do AC small signal analysis of a BJT transistor with dV/dI ~ re = 26mV/Ie. But I don't understand why we take Vbe as 26mV here. Also, in the datasheets, I found graphs of input/output ...
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Non-linear behavior of the transistor and many other questions got me desperate. Help me design a class A amplifier

Firstly, no. This is not an assignment. Indeed I passed the Electronics class with a high mark last year. Out of curiosity, I decided to design a class A amplifier with a 2N3904 transistor, because I ...
İbrahim İpek's user avatar
1 vote
1 answer
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Would more connectors introduce more noise for low-frequency current signal?

General question When measuring the weak amplitute low-frequency (DC) current signal (in 0.1 - 1 uA) transmitted through FFC cable and connectors to a PCB with transimpedance amplifier (TIA) and ADC, ...
Yuanyi Wu's user avatar
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Differential and common mode MOSFET

I am studying this problem and its solution: There are some concepts I don't understand: How did the output voltage when vi = 20mv become this? I already got ADD and Vo, I just don't understand how ...
Aeden Schmidt's user avatar
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3 answers
143 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?
South goodman's user avatar
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2 answers
238 views

How feedback loop is done in wide voltage range laboratory power supply? TL494 compensation

Hello i would like to ask how is compensation done on switching PSU with wide range variable output voltage (from zero to several hundres of volts). I have succesfuly (I guess) simulate my own design ...
LinejHonzaCZ's user avatar
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1 answer
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Transfer function of a system regulating current

Here is the circuit with two different MOSFETs : The circuit controls the current through the resistors R3 or R1 via a reference voltage (V1 and V3). As you can see there is an inductor. I plot the ...
Jess's user avatar
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Small signal model of buck converter

I want to find the transient response of an open loop buck converter for a step change in load current. To obtain the output impedance Zo = vo/io, which would help me to find the transient response of ...
ritvik rathore's user avatar
2 votes
2 answers
285 views

Return/Ground signal between SMA output

I am designing a IRIG-B AM modulated circuit. IRIG-B output signal will eventually be connected to another box (takes my IRIG-B signal as an output) through a wire (probably more than 4 feet). ...
nmr's user avatar
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166 views

Effect of GBW and slew rate for "small signal"

I would like to better understand how to choose an op amp for high speed application and more precisely I would like to better understand how the GBW and the slew rate influence the transient response/...
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AC analysis of SMPS shows instability. How to modify the analysis to reflect the transient stability?

Background I have designed a switch-mode power stage with voltage-mode control that uses an LCLC filter in its output to obtain a very low ripple output voltage. I have empirically arrived at a ...
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How do the stages of this high pass filter work?

I am trying to understand exactly how the stages of this Moog high-pass filter work but I still have several things that I cannot quite figure out: Q13 and Q14 form a push-pull amplifier, and are ...
charis's user avatar
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2 answers
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BJT amplifier: small-signal analysis using H-parameters

I'm preparing for an exam and I have this problem where I need to find the input resistance as it is seen by the voltage generator ug. After using H-parameters to find an equivalent circuit I came up ...
3d014's user avatar
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Please help me draw the small signal model of this circuit

I am trying to draw the small signal model of this circuit. I am not sure if it is correct that I connected VB (Vbias) to the ground in the small signal model since it is a supply voltage (please ...
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Why do JFETs have such wide parameter spread?

I've noticed that in almost every JFET datasheet I've looked at, the values for Idss and Vto (also known as Vgs-off vary hugely. A J111, for example, could have a Vto of anywhere from −3 to −10 volts ...
000's user avatar
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1 answer
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How to calculate small signal gain with LTspice?

For my homework I need to find the small signal gains of the circuit below. For the first part of the circuit the small signal gain is calculated with $$A_{V1} = \frac{u_{a1}}{u_e}$$ and for all of ...
Efe's user avatar
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2 answers
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Can you explain intuitively why the pole exists in this common-emitter circuit?

This shows mathematically that common emitter circuit with the bypass capacitor \$C_e\$ has a pole. Can you explain intuitively why the pole exists here?
internet's user avatar
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How to calculate the Output Impedance of RoT1?

I am a student, and I want to calculate the small-signal analysis, but I don't really know what's the formula of RoT1 (being a degenerated common base with RoT1 in the collector).
EngineerMan's user avatar
4 votes
5 answers
2k views

Why is the frequency response of an LED important?

I'm working on visible light communication where I fabricate my own organic LEDs. One of the ways to characterize them is "small signal analysis." I understand we are applying this analysis ...
LifeIsBeatiful's user avatar
1 vote
1 answer
217 views

Definition of small-signal capacitances calculated by Sentaurus TCAD Mixed-Mode/AC Analysis

I'm currently working on a capacitance model which will be part of a greater compact model for a planar RFET. I use Sentaurus TCAD to generate capacitance data, which I use to understand the ...
zraibra's user avatar
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2 answers
486 views

Small circuit analysis, DC voltage source short circuit or ground?

To convert a BJT into a short circuit we know that all DC voltage sources are short circuited. Yet my professor did this: Isn't this a contradiction? I just can't grasp the step.
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Series capacitor buck converter small signal model

Does anyone know how to do the small signal model of the series capacitor buck converter? I can't find a related paper talking about this one. I think the small signal model is not the same as the ...
Power JJ's user avatar
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2 votes
1 answer
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Is there a typo in this question because I don't think the emitter node of Q2 should be grounded?

In this problem, it's asking us to draw the small signal equivalent of an amplifier but I think the answer they gave is wrong. In the second picture (b) I don't think the emitter of Q2 should be ...
snowball's user avatar
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Small-signal of CS stage with source degeneration

Can someone explain how Fig 3.30 (c) was created? In particular, the \$\large\frac{1}{g_m + g_{mb}}\$ resistor to GND. I know you see \$\large\frac{1}{g_m + g_{mb}}\$ when looking into the source, but ...
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3 votes
1 answer
814 views

Wilson BJT current mirror output impedance

I am trying to have a small signal analysis of a Wilson BJT current mirror to find out what is the output impedance. Already I know that the answer is $$R_o=\beta r_o/2$$ In the first step, I need to ...
chami's user avatar
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1 answer
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Is the "\$\small o\$" in \$r_o\$ short for output or number 0?

You usually see ro in the small-signal models of BJTs or MOSFETs like this. I'm curious if the "o" there is short for "output" or just the number zero? I think I saw people reading ...
internet's user avatar
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3 votes
3 answers
641 views

Derivation help: gain of 2 NMOS in series

I am trying to find the gain (Vout/Vin) of the circuit below, this is not a real circuit that I have, I am just trying to learn more about circuit analysis. The circuit reminds me of a cascode circuit ...
Josh Girgis's user avatar
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1 answer
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Dupicate LFO Signal and Invert, keeping MAXs and MINs

Im working on a Dual LFO with "Depth" and Rate controls. I already got the "root" LFO signal working and if I do this, I can generate the LFO swinging from 0v to 9v... and with ...
ElectronOne's user avatar
1 vote
1 answer
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What is wrong with this MOSFET differential pair analysis?

I am confused regarding the analysis of the circuit on the left and its small-signal equivalent circuit on the right: simulate this circuit – Schematic created using CircuitLab Here is my ...
Wais Kamal's user avatar
2 votes
3 answers
195 views

How does a BJT differential amplifier amplify?

I am reading The Art of Electronics. I found a related question here. I understand that differential gain of the amplifier is $$G_{\text{diff}}=\frac{R_c}{2(r'+R_e)}$$ but how? OK, using hybrid-pi ...
TheUnknown's user avatar
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2 answers
374 views

Flyback converter small-signal model

I am currently designing a flyback converter and I am interested in measuring the stability of the converter (with a Bode plot). I will try to connect an isolation transformer on the feedback loop ...
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