Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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").

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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Charge, Voltage, or Current? What can be measured with the highest SNR?

Suppose I have a Faraday cup and a certain number of ions hit the detector. What is the highest signal to noise ratio way / circuit to measure this... does one measure the charge (coulombmeter), voltage (voltmeter), or current (ammeter)? Is there…
seven68
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mV variations even with a simple voltage divider

edit: After using a prototype pcb instead of breadboard, placing all possible electromagnetic sources away and unplugging all the equipment from the same line, my noise dropped 2 orders of magnitude. The main thing that changed the game was pcb and…
kudagaci
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Re model for Collector feedback bias with emitter resistance

For the given NPN transistor with \$\beta=99\$ and \$r_e=0.02 k\Omega\$, I need to find the voltage gain using Small signal Analysis. I drew the equivalent \$r_e\$ model as below. To find the Voltage Gain \$Vo/Vi\$, I First went from \$Vi\$ to…
Equation_Charmer
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Finding Rout of differential pair with active current mirror (from Razavi's "Design of Analog CMOS Integrated Circuits 1st Edition")

According to Razavi, \$R_{out}\$ is approximately \$r_{o2}||r_{o4}\$: I get the same answer (assuming \$2r_{02} >> \frac{1}{g_{m3}}||r_{o3}\$): But how did he get equation 5.27? In particular, how is \$I_{xy} = I_{d4}\$. I.e. how did he get the…
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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 at Vds = 5 V and Id = 1 A, while the J112's Vto…
El Ectric
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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 to see the bandwidth of the OLED, but I do not understand…
LifeIsBeatiful
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Diode-connected transistor, small-signal, Norton, Thevenin

How do I calculate the equivalent Thevenin resistance of the small-signal model of a diode-connected transistor (base tied to collector)? Early-effect is neglected. The port of interest is between C and E. In the figure, \$v_{\pi}\$ is the…
M_E
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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 with simplis (picture #1). I am using TL494 which…
MacIntoshCZ
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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 draw the small signal model. My model is…
chami
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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 where the gates are the same potential instead…
Jirhska
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What is DC small-signal transfer function?

Can someone please explain to me what is the DC small-signal transfer function? I found this analysis type in LTSpice and I have no idea what it does! My guess: It linearizes the circuit around the operating point and then basically computes the…
user2276094
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Impact of PFC output impedance on the regulation of a converter

I have determined the transfer function of my converter operating in closed loop configuration. Nevertheless I saw on the web that the transfer function is not the same if my converter follows a PFC. This refers to the Extra theorem element and the…
Jess
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Adding a Delay Ltspice

Is it possible to set a delay between two components on Ltspice ? Actually I just want to simulate the time for a sensor it takes to react (set an output) to an exciting signal. This is for taking into account the impact of a delay with respect to…
Jess
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Solving a simple single-ended differential amplifier

simulate this circuit – Schematic created using CircuitLab N.B. I_D=KVov^2 without the 2 I’m really confused with this excercise, my problem is to calculate the A_v=v_out/vd and the cutting high frequency fH neglecting the parasites capacitors of…
Sergio Piccione
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What is the difference between DC base current and signal current in CE transistor amplifier?

I came across a sentence that " if the DC base current has to be 10 times the signal current....".I could not understand, what is DC base current as I have just read about Input current and Output current? And also what quantity (like current…
Star on earth
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