# 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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### 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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### 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 ...
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 ...
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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### 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 ...
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 ...
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### 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 ...
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### 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 ...
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
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
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### 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
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 ...
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 ...
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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### 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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### 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 ...
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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### 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 ...
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 ...
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1 vote
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### 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 ...
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 ...
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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### 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 ...
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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### 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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### 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
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 ...
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### 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 ...
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 ...
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
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### 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-...
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### 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 ...
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 ...
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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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 ...
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### 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
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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### 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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### 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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### 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
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:...
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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...
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