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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Impact of Input Capacitor on the Derivation of the Small-Signal Model of the Buck-Boost Converter
I have been studying the control methods of DC/DC power converters over the past couple of weeks and am confused on how the addition of an input capacitor affects the small-signal model of the buck-...
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Does Rbe is equivalent to Rpi of the small signal PI model?
I have a question about the bipolar transistor model (and behavior) :
I would want to know if the Rbe of the transistor is the equivalent of the Rpi of the small signal Pi model ?
if it's the same, do ...
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Small signal analysis confusion: which zero load condition should I use?
Which zero load condition should I use when trying to find Ri?
Zero load, defined in our class, is when \$I_{out}=0 \space or \space V_{out}=0\$. I was trying to solve this current mirror circuit, and ...
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Why does parasitic capacitor have no effect on the output side of amp?
This post will be refering to two books, look at the end for complete descriptions.
My question is about simplifications to the small signal model of a BJT voltage-to-voltage amp. This particular ...
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Is it possible to find bandwidth without r0 in small signal hybrid-π BJT?
I am finding the bandwidth of hybrid-π BJT. This picture is from my tutorial. If I have gm,RB,RL,Cπ,rπ,Cμ, is it possible to get bandwidth without r0? As what I understand, if need Cin using Miller ...
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I designed an Op Amp but the feedback loop would not generate the expected behavior
I have designed the following operational amplifier as my final project of the Analoge Amplifiers subject.
It consists of a differential amplifier as input stage, then there is a common emiter ...
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What is the current through this resistor in small signal analysis?
This is circuit below (Note: \$V_T\$ is the AC signal)
Is the current through this transistor 0 in small ac analysis?
Does this equation below hold?
$$-V_x g_{m1} + \frac{V_F - V_X} {r_{o1}} = 0$$
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Why remove load resistance for DC analysis in transistor amp?
I'm currently studying electronic devices. I've reached transistor amplifiers. The image above shows a common-source amplifier. I'm confused about why the textbook takes the load out for DC analysis. ...
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Equivalent impedance seen into drain
I can't understand or simplify the Zx in the picture
is equal to that of
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What's the current direction through cap in this small signal analysis of this first stage amplifier?
Consider the circuit in this netlist. Assume all transistors are operating in saturation, \$V_{Tn} = │V_{Tp}│=V_T\$,
\$\lambda ≠ 0\$ but \$\gamma = 0\$ (neglect body effect). Neglect all parasitic ...
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How to calculate the voltage gain of a circuit with P-MOS and N-MOS transistors?
I was asked to calculate the voltage gain of a circuit containing 2 P-MOS and one N-MOS transistors:
I calculated the operating point and got: gm1 = gm2 = gm3 = 2 [ms]
The circuit that I built for ...
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Question about Ridley's peak current mode control model, why the L in small signal model can be seen short-circuit when driving Kf'
I have a question about Ridley's way of deriving Kf' in his PHD paper: Why can the L in the small signal model be seen as a short-circuit? L can only be seen as short-circuit when calculating DC gain, ...
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Cascode transistor small signal analysis
I could not find a similar question on stack exchange and I need pretty urgent help.
I am confused about how to represent this circuit using small signal model for the transistors. Particularly R2, ...
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Small signal model from two transistors stage
I'm looking for help to find the equation of Vout of this design. I tried to do small model equivalent circuit and equations using with KVL. But I can't find the way to solve my system of equations, ...
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Superposition principle and Small signal analysis
first of all the superposition principle states that
$$[ f(ax_1 + bx_2) = af(x_1) + bf(x_2) ]$$ and this apply to all linear element like resistor and capacitor because if we considered the current to ...
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Question about drawing the small-signal equivalent circuit of an amplifier exercise
From Razavi's Fundamentals of Microelectronics book:
I don't understand where did this ground come from?
The resistor r_pi2 is connected between the emitter and base and then the base is grounded (...
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Help Needed with Compact Circuit Design for Pulse-Triggered Switch-Off Sequence
I am currently working on a small electronics project for my swimming club and could use some advice. Forgive me if this is basic, I'm really new to electronics.
The project requires a compact circuit ...
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3 phase emi filter for analog signal
I'm developing a device that needs to read analog data from a sensor located far away (~ tens of meters).
To eliminate conducted noise (150 kHz..80 MHz) I use a ferrite filter on the cable and ground ...
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Resistance in the small signal model of a MOSFET
I have a question about the small signal model of MOSFET. As you know there is a voltage-controlled current source in the model. I've seen somewhere in books that we can replace it with a resistor ...
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Switching circuit with logic 3.3V control on p-channel JFET
The task is to derive sinewave (of higher frequency) chopped by step-function (also periodic but of lower frequency, i.e. several periods of sine wave are placed in that pulse). So I have a sinewave ...
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I don't understand the small signal model of this circuit
I have a book that contains the solutions to certain problems that states that the small signal model for this circuit:
is this:
I don't understand it. Why is \$Z_L\$ in parallel with the VCVS \$...
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What is the difference between a BJT's DC and AC gain and why are they different [closed]
Could you please explain what is the difference between the DC and AC gain of a BJT and why is the gain different for DC and AC? Where would the different gains be used?
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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 ...
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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 ...
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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....
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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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, ...
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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?
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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 ...
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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 ...
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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 ...
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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). ...
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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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