Questions tagged [small-signal]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
3
votes
0answers
107 views

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. ...
0
votes
0answers
39 views

Making an operational amplifier out of a differential pair

I need to modify this circuit to serve as an operational amplifier with low output resistance Because the operational amplifier that I'm familiar with uses this differential pair: I thought about ...
0
votes
0answers
25 views

Proving that we can apply the half-circuit model for the common-source differential amplifier

This is the circuit I'm trying to solve through the half-circuit model: To do so I need to first prove that \$V_{p}\$ is a small-signal ground under opposite symmetric excitation (\$v_{in1}=-v_{in2}\$...
0
votes
0answers
41 views

Confusion with Norton's equivalent

I was trying to find Norton's equivalent for the following circuit from A to B: So I decided to start by using the fact that \$R_{th}=V_{OC}/I_{SC}\$, and found out that \$V_{OC}=0\$ so I decided to ...
1
vote
1answer
72 views

How do I get a KCL equation involving Vin in this circuit?

simulate this circuit – Schematic created using CircuitLab I've been scratching my head with this one. The circuit below is a small signal equivalent circuit of a PNP CB amplifier. I'm trying to ...
2
votes
1answer
73 views

Small signal Forward converter

I am back again on this subject. I found the control to output transfer function (Iout/Vc) of my forward converter (current mode) which is particular as it is without output capacitor. Actually it is ...
0
votes
1answer
46 views

What is the control Input of the small signal current mode PWM switch

I am trying to simulate the open loop transfer function of my system. My system is really classic. A converter (the plant transfer function), a sensor and a corrector which is a simple Integrator (1/(...
3
votes
1answer
45 views

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 ...
0
votes
0answers
35 views

Buck converter small signal model

Hi Recently, I am using the buck converter to charge the battery, and I am confused, how to model the buck converter in small signal, when load is a resistor, I can know the duty to output, duty to ...
0
votes
0answers
43 views

Why is this small signal model incorrect?

Here is the model I was told to redraw by replacing the transistors with their mid frequency small signal model: And here is my attempt at doing so: Upon receiving feedback, I was informed that the ...
1
vote
0answers
29 views

How to get the minimum transconductance of a BJT ce amplifier?

We are being asked to bias a ce ampilifier circuit above to a gain of 15. It is given that the DC supply voltage is 10 V and a Vce,sat = 0.3V. Assuming that ro >> Rl >> Rload (on Vout when ...
1
vote
1answer
62 views

Small signal model of a forward converter operating in current mode control

By knowing that I do not know the plant transfer function of the forward converter operating in current mode control, I can be suspicious on the result provided by the following document : https://...
0
votes
0answers
52 views

Missing information when calculating impedance via Blackman's theorem

The AC course at my university has an ex-exam question where, in the below circuit, the impedance w.r.t. ground has to be calculated for the rightmost node. The question asks to do this using a test ...
0
votes
0answers
44 views

how to find Vout/Vin in this circuit? BJT frequency response

I have been struggling for 1 hour trying to relate Vout to Vin. However, I truly cannot. I tried KVL, node analysis etc everything that I could. Can you help me pls? The topic is frequency response of ...
0
votes
0answers
50 views

Where does this resistor appear in my nodal analysis? [BJT small signal analysis]

Here is my small signal circuit of a PNP common base amplifier with a resistor Rin at the emitter, Rl at the collector and a voltage source Vb at the base. Here is my large signal circuit: simulate ...
0
votes
0answers
39 views

Small signal gain

I'm struggling to find the small signal gain of the circuit shown below. I am trying to find the gain from Vout to Va. Note that Vout corresponds to the output of an amplifier. Any help is much ...
2
votes
4answers
257 views

Why does a circuit model of N-MOSFET exhibit a finite resistance between source and gate?

In the T-equivalent circuit model of a MOSFET in small signal analysis the MOSFET shows an infinite resistance between its gate and source when looking from the gate while it shows very little ...
0
votes
1answer
49 views

Small signal analysis of BJT dynamic microphone preamplifier

I am trying to do a small signal analysis for the following circuit I did not have any experience with BJT so I am having a hard time to analyze the circuit. From research, I know Q1 is common base ...
2
votes
1answer
77 views

Small signal analysis of dynamic microphone preamplifier circuit

I am trying to do a small signal analysis for a dynamic microphone preamplifier circuit. The original circuit is using BJT but I did not have much experiences with BJT, so I switched all BJT to MOSFET....
1
vote
0answers
42 views

short circuit time constants method (SCTC)

Why does the short circuit time constants method (SCTC) apply to large valued capacitances used for coupling or bypass purposes in a small-signal amplifier?
0
votes
1answer
121 views

Derivation of Feedforward Gains for current mode control in CCM converter

I recently start to read the dissertation of Dr.Ridley, A New Small-Signal Model for Current-Mode Control and I am stuck on a basic equation. First we have the function of the inductor current for ...
0
votes
3answers
152 views

Art of Electronics 2nd edition p. 67, figure 2.8 — what causes the clipping?

I have been rereading this section and realized I always get hung up here. The idea of clipping happening because the emitter is not able to stay .6 or so volts less positive than the base is ...
-1
votes
5answers
113 views

Why does the feedback mechanism linearize the vi vs vo characteristic curve?

For a unity gain configuration opamp, we arrived at the conclusion that vout = vi * A/(A+1) by using small signal analysis, since A here is the small signal open loop gain. My question is: Why does ...
0
votes
1answer
96 views

How does the Common Emitter amplifier ensure low distortion?

My understanding of a small-signal amplifier is very limited. From what i've understood from this article is that for a BJT in the CE configuration, it provides minimal distortion at the output, I ...
0
votes
0answers
76 views

Small signal analysis - Flyback transfer function - LTspice

I am trying to simulate the transfer function of a Flyback by using LTspice. The flyback that I am trying to simulate is a flyback which can be found into the book "Switch mode power supplies&...
0
votes
1answer
39 views

What is RB in this CE circuit?

I'm working through this handout I3.PDF to help me understand feedback in common emitter amplifiers. (The author does not reveal his/her name in the PDF and so I can't ask them directly.) They show ...
0
votes
1answer
54 views

Optocoupler ac model ltspice

I am trying to plot the bode diagram of a flyback converter on LTspice. This is the first time that I do this and before trying to plot my flyback converter, I would like to plot the bode diagramm of ...
2
votes
1answer
66 views

Op Amp Selection Help for Rail/ Rail IO

I am looking for an operational amplifier which will fit my requirements. My circuit consists of two cascaded non-inverting amplifiers.I have a classical non-inverting setup.The minus pin of both ...
0
votes
2answers
35 views

Can I produce small signal gate-source voltage by applying small signal source-drain current?

As stated in the title, Can I produce small signal gate-source voltage by applying small signal source-drain current? There is no doubt that I can produce Ids by applying vgs, what about the other way ...
0
votes
1answer
61 views

Degenerated common source output resistance by inspection

In Razavi's Design of Analog CMOS Integrated Circuits (2nd edition), on page 65 he describes a way to derive the output resistance of a source-degenerated CS stage by inspection: I understand how to ...
3
votes
1answer
82 views

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 ...
1
vote
1answer
110 views

Why does a Darlington pair have a higher input impedance compared to a regular normal BJT transistor?

Freshman here, and I've been searching for an answer to this question, but I could not find any actual justifications yet. Basically, I am studying the concepts of a Darlington circuit, and saw that ...
0
votes
0answers
148 views

Degenerated Differential Pair voltage headroom

I was reading about ways to make the differential gain linear by adding degenerative resistors Rs as shown, but it has voltage swing limitations, having swing reduced by Is*Rs( when one of the MOS ...
1
vote
0answers
55 views

BJT Amplifier Circuit Analysis Feedback

I've been reading up on small signal analysis to try and better understand audio amplifier circuit design (end goal a discrete BJT guitar amplifier). I'm attempting to apply the knowledge I've picked ...
0
votes
0answers
78 views

Basic MOSFET small signal model with no load and Rd

I've come across the most basic small signal model of the MOSFET. We have a NMOS whose drain is connected to Vdd= 5V and source is grounded. We also have biased gate with a DC 2V. Suppose the ...
6
votes
1answer
176 views

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), ...
0
votes
1answer
132 views

Z(out) for small signal analysis with BJT for unbypassed emitter and r0 in place

from this BJT small signal I try to solve Z(out) but I find RC || (ro + RE) because Z(out) is calculated with ib = 0 => beta ib = 0 from this link too V(in) was calculated But the expression for ...
1
vote
0answers
29 views

BJT Hre simulation problem

im having problems understanding the behavour of the hybrid parameter hre in the bjt AC model. im using the pi equivalent circuit to simulate the relation between hre and Ic (Dc value). i am not ...
0
votes
4answers
89 views

Proof of linearity of a transistor

When we deal with a transistor we break it up into two parts, 1 The DC bias. 2 The small signal perturbations. Then we add the currents/voltages from the both the analysis to get the total response. ...
1
vote
1answer
54 views

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 ...
2
votes
2answers
45 views

Base current in a npn transistor in view of its small signal model

We know that in a forward biased transistor we have βIb = Ic. However in the model it's clear that the above equality doesn't hold, we now have Ic > β.Ib. What's wrong in my understanding of the ...
0
votes
1answer
38 views

Input and Output Resistance of an Amplifier

I attempted to find the input resistance by using the thevenin equivalent circuit. I shorted all the capacitors and changed the circuit to its small signal equivalent. I found Rb to be 13.33kOhms ...
0
votes
1answer
54 views

re model of transistor

In which case shall I consider output resistance(ro)? I found that in case of re model for common emitter configuration we are considering output resistance(ro) but there is no (ro) in emitter ...
0
votes
3answers
136 views

Do capacitors and inductors have initial voltage or current in small signal approximation problems?

I'm trying to solve a small signal approximation problem. The operating voltage for the capacitor is 2 volts. I simplified capacitor by a linear one. In solving this problem should I consider the ...
0
votes
2answers
81 views

is this small signal equivalent circuit of mosfet amplifier correct?

We are given an assigment about mosfet common source amplifiers and we are given this circuit. I drew its small signal equivalent circuit but I am so unsure about placement of ro(transistor resistor). ...
6
votes
2answers
4k views

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. ...
0
votes
1answer
34 views

Where does the input resistance formula of a BJT amplifier come from?

I just solved the (a) question of this problem from one of my past exams. And I am a bit confused on to why the solution is as follows: Rin = 100kΩ || Rib Rib = (rπ + (1 + β)Re) And the way Rib is ...
1
vote
0answers
33 views

Differential Amplifier small signal analysis

I am having trouble doing the analysis the small signal model of this circuit: So far, I have come up with this this circuit for the small signal analysis: However, I can't come up with a formula ...
0
votes
2answers
124 views

MOSFET small signal model output resistance

I am wondering what is the output resistance of the circuit below. I found that it depends on the gate voltage: $$ \begin{aligned} R_{out} &= \frac{V_{out}}{I_{out}} \end{aligned} $$ $$ \begin{...
0
votes
0answers
46 views

Strange MOSFET Common-Source with RD=0

I was trying to solve this circuit(find the Q Point, voltage gain, input and output resistances in midband region, the lower cutoff frequency using SCTC method), but I was confused by the absence of ...