Questions tagged [circuit-analysis]

Circuit (Network) analysis is the process of finding the voltages across, and the currents through, every component in the network.

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3 votes
4 answers
186 views

Solving for elements of a conductance matrix, given the voltages at each node

I'm trying to solve for the elements R12, R14, R23, R34 in the following circuit. Resistances to ground R1, R2, R3, R4, voltages at nodes V1, V2, V3, V4, and input current I0 are all known. The ...
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0 votes
1 answer
43 views

12V, 5A ""CHOPPY" - PWM - Giving 10-12V Range output?

I have the following circuit built from the 'choppy' pwm controller kit. However upon testing it, it only ranges the voltage from 10-12V. How would one analyze the circuit shown to confirm this is ...
-2 votes
2 answers
86 views

Super mesh analysis [closed]

Please someone help me to write mesh equation.I don't know whether i should consider both the current sources to write first equation or only the independent current source.A current source is in ...
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0 votes
2 answers
108 views

Find input impedance in calculation and simulation [closed]

May I ask how to find the input impedance for the output of VG1 in the calculation and in simulation tests? Should I consider the op-amp as a resistor with the ideal input impedance when calculating? ...
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0 votes
2 answers
82 views

Output voltage of a step-down voltage regulator (or buck converter)

I've the following step-down regulator: and I'm wondering how to get the following formula for the output voltage: $$ V_{OUT} = \frac{T_{ON}}{T_{ON} + T_{OFF}} \, V_{IN} $$ I calculated the current ...
0 votes
1 answer
40 views

Low voltage from simple PWM circuit

I'm attempting to make a simple PWM speed controller for a fan motor. I am powering the circuit with a 12V 10A PSU and have successfully tested the motor directly connected to it. When connecting the ...
2 votes
3 answers
112 views

What are the rationales behind real wire (transmission line model), real capacitor and real inductor model?

I have been pondering about how the real model of circuit elements (wire, capacitors and inductors) and transmission model are derived through intuition (based on physics). Here are my references from ...
0 votes
2 answers
115 views

Do you understand this circuit?

I'm trying to reverse engineer this circuit so that I can use the buttons with a microcontroller. The problem is with buttons on the left. Counting from right to left, above on pin 7, I think that's ...
2 votes
5 answers
92 views

What does the diode do in this LSO (Low side output driver)?

I have a GCM196 with and I am trying to Ground a signal using a Low Side Output. There are pins with and without a diode. What does the diode do in this circuit?
1 vote
0 answers
134 views

How can I identify these two electrical components?

Could you please help me in deciphering these two electrical components? I can provide schematic as well. enter image description here
0 votes
1 answer
102 views

Series voltage regulator with Zener diode and BJT - equations to explain the working principles

I'm studying the following series voltage regulator, and I'd like to know how to "prove" the last two sentences by using equations. For example, in the case of the 2nd sentence, the first ...
1 vote
1 answer
77 views

How to model a circuit with resonant inductive coupling?

I need to model (write the equations for) a circuit with resonant inductive coupling, such as the one in the picture below. The picture is taken from the Wikipedia article on Resonant inductive ...
0 votes
0 answers
47 views

Two port network analysis

I'm trying to find the Y matrix and getting stuck. Y11 and Y21 were correct but when I assumed Vo = 0, I didn't know how to continue... (assume gxr<<1)... I tried to move to the next question ...
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0 answers
70 views

RC-circuit transient SPICE simulation diverges after adding one capacitance

I tried to build a lumped parameter RC circuit model for an induction machine. The SPICE simulation worked fine for a steady state with no capacitances. Then I tried to add capacitance one by one as ...
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0 votes
5 answers
109 views

What's the difference between these two circuits? They both work

I'm a beginner. These two circuits are the same, except one has the resistors placed above and the other with the resistors placed below. They both have the same current going through, except the ...
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4 votes
0 answers
100 views

Can this Raspberry Pi UPS circuit work?

I created following UPS circuit to shutdown my Raspberry Pi 3A+ properly: I would really appreciate if somebody can review my circuit. I know it's a little bit hard to read, but I'm sorry. I'm a ...
0 votes
0 answers
47 views

Can I make GND vias like this under my QFN package?

Can I make GND vias like this under my QFN package?
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2 votes
3 answers
402 views

What is this component marked 5R1 with designator F12 and what value is it?

I am repairing a sound board and I cannot figure out what it is. The SMD says "5R1" on top for 5.1 ohms. I cannot tell if this is a fusible resistor or a varistor. Varistor Symbols cut up ...
0 votes
1 answer
67 views

How to measure the power of two small solar panels independently and combine the power?

I am trying to make the connection below. I want to measure the voltages coming from the solar panels connected to pins 2 and 3 and then deliver their combined power at pin 1 in the teal square. I ...
1 vote
2 answers
49 views

Difference between application of series and parallel (grounded) capacitor

I wanted to understand the difference of the two applications shown in the picture below, one is in parallel (grounded) which, as far as I know, is used as a bypass capacitor used to remove the high ...
0 votes
0 answers
32 views

Input referred noise of two port networks

I am given some noisy black-box two-port networks whose Y-parameter & output noise spectrum is known (when output is open or short). I need to find the input referred noise for: Each individual ...
0 votes
2 answers
82 views

What should I do to find the Thevenin voltage and resistance for large circuits?

I have the following circuit and I'm asked to find the Thevenin resistance between points A and B. I tried to solve it by creating an open circuit between the points, as usual, thus removing the ...
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0 votes
1 answer
83 views

LC circuit with back to back diodes [closed]

I know how an LC circuit works, but in this circuit there are 2 diodes and I am not able to intuitively get the waveforms of current and voltage across the capacitor. Could you please help understand ...
5 votes
3 answers
894 views

For below circuit, the simulation result is not matching with theoretical prediction

Please note that i1(t) is the loop current (in loop analysis method) and not the inductor current. The answer to above problem is option B, which is derived below Following principles are used: ...
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0 votes
1 answer
90 views

Why does this capacitor make the measured voltage higher than supplied?

I had a situation where a capacitor was installed in series instead of the intended resistor. When measuring with this cap in series it measured like 5 volts. When changing the cap to a 24-ohm ...
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0 votes
2 answers
40 views

The structure of the loaded circuit in Thevenin's theorem

If the load in Thevenin's theorem happens to be a circuit instead of a single resistor, must this loaded circut contain only resistors or may it contain also voltage or current sources, etc.?
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1 vote
1 answer
40 views

Measure L sweeping frequency

I have found the circuit below as a method to measure inductance. My understanding is that we do a frequency sweep with the 555 timer. The LC tank, which is connected to the timer, will resonate at a ...
0 votes
1 answer
83 views

Why is there current flowing through the resistor R1?

I came across this problem in a book. In the question, one has to determine the current through resistor R1 as a function of the input current, while assuming a constant voltage model for the diode D1 ...
-2 votes
2 answers
67 views

Norton's equivalent circuit - current through short circuit

In this tutorial, the tutor is finding current through 12 ohm resistor using Norton's theorem. My question is: When 12 ohm resistor was replaced with a short circuit, why entire current (15-I1) isn't ...
0 votes
2 answers
91 views

How can I understand amplifier types?

I am studying for my final exam. I am struggling a bit with the frequency response formulas. For instance like this circuit, the formulas generally are the same. I don't know what type amplifier it ...
1 vote
3 answers
62 views

Node voltage - I am having trouble making my system of equations

For the problem, I need to find the voltage of the two nodes on top. I am using the node at the bottom as the reference node. When trying to make my KCL equations I came up with: v1/60 + v1/15 + (v1-...
0 votes
2 answers
55 views

How to find an equivalent LC circuit from a combination LC circuit [closed]

I have a circuit containing a number of L and C, both in parallel and series. How can I find the equivalent LC circuit (with a single L and C) for such a circuit? Kirchhoff or Thevenin can give me the ...
0 votes
0 answers
36 views

How to design, build and test synchronous sequential circuits using T-Flip Flops?

I want to Use T flip-flops to design the circuit specified by the state diagram of following figure. Zi represents the output of the circuit. This is my school project. I did everything. But I cannot ...
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0 votes
1 answer
101 views

Converting 3.3V logic to 5V logic with two common emitter transistors in series

I am working with digital signals. I would like to know if there is any alternative to boosting a 3.3V logic signal to 5V logic only using transistors. I am currently using two common emitter ...
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5 votes
2 answers
761 views

Problem with equivalent resistance

I have a problem determining equivalent resistance of this circuit. The previous assignment had the battery between C and 3R1 resistor, and i knew how to calculate the equivalent resistance. I ...
0 votes
0 answers
42 views

RMS current for capacitor after placement of TVS diode

Following circuit is a part of the product and capacitor C2 and D2 were damaged due to very high current high frequency transient noise. I am simulating the circuit by coupling the high voltage AC ...
1 vote
4 answers
195 views

Synthesizing an impedance given by transfer function (poles/zeros) using a passive network

I would like to synthesize an arbitrary passive network based on a given transfer function (poles/zeros). The origin is the output impedance of a voltage regulator for which I want to find an ...
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0 votes
1 answer
80 views

Why is the voltage drop being used to calculate the current?

I need some more help with explaining an example. I'm having trouble understanding this part of a tutorial, and my question is fairly simple. Why use the voltage drop rather than the battery voltage ...
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2 votes
1 answer
73 views

Can anybody explain these examples?

I am just getting started with electronics coming from a web dev background so this is a beginner question. I am following this tutorial and I'm confused about this part! The paragraph under step 4 ...
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3 votes
2 answers
302 views

How to analyze this RC circuit without finding Thevenin's equivalent circuit?

simulate this circuit – Schematic created using CircuitLab I want to find capacitor's voltage equation in this circuit (\$v_{C}\$) knowing that the capacitor is initially uncharged, I know that ...
1 vote
2 answers
150 views

How to include result of RC circuit at t = 0?

For the answer to the problem below, if I want to include the result at t = 0 as well should I write it as? I don't know if it's possible to combine them into one expression only. Here is the problem:...
-1 votes
1 answer
43 views

Creating equivalent impedance for given measured frequency response (that does not involve blind trial-and-error)

I have a measured frequency response and I would like to create an equivalent impedance model for it. I start with a parallel RLC and then add series R and series L to the elements. I blindly tune the ...
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2 votes
2 answers
169 views

DC analysis of a BJT circuit with base feedback

I'm trying to analyze a bigger circuit and trying to figure out the DC voltage at the collector. I narrowed it down to this much simpler circuit, which outputs 1.379 V. I cannot seem to get the same ...
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-1 votes
1 answer
127 views

How to divide 15V to 12V and 3V?

I need to get both 12V and 3V from the same 15V source as outputs, but can't seem to do it. Can someone please help?
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0 votes
0 answers
51 views

Keyboard LiPo battery charger schematic review

I am designing a wireless keyboard, currently working on the schematic. I have been looking at MAX17330 Charger IC. Here's the datasheet. When USB is plugged, it should charge the battery and power ...
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0 votes
1 answer
56 views

How doest this PSC multi-speed motor circuit work?

I've been replacing the thermal fuse of my fan blower each time it trips (every year or so, when the oils degrades). But this year I decided to look at how the motor works. It has 3 speeds (slow, ...
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-2 votes
2 answers
186 views

Why is the voltage measurement accross this resistor 0v? (TinkerCad) What's wrong with the circuit?

Please help me understand why the voltage measurement across the Zener diode and resistor is 0V. How should I go about getting a 4V reading there? If you notice other problems, or have some ...
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0 votes
2 answers
109 views

When I do a simulation in LTspice I receive errors

When I run the simulation I receive errors. I am a beginner in Ltspice and I do not know how to solve this problem. I have to draw from 1 to 6
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4 votes
3 answers
1k views

Why does does the power supply in my op-amp circuit need to be connected to ground?

In another question a user posted the following circuit. simulate this circuit – Schematic created using CircuitLab It was explained to the user that the op-amps negative supply rail should be ...
2 votes
1 answer
64 views

Which matrix index should be used when Y (admittance) is shown to compose a circuit segment mapped to an ABCD matrix? Y21? Other?

I would like to cascade a serial capacitor with a shunt inductor to form an L-match network by multipling two ABCD parameters and convert the result to S-parameters that represent the composite ...
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