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# Questions tagged [circuit-analysis]

Circuit (Network) analysis is the process of finding the voltages across, and the currents through, every component in the network. Consider using in conjunction with tags for the particular analysis technique(s) in question: "nodal-analysis", "mesh-analysis", "superposition", etc.

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### Problem with Capacitive Feedback Amplifier

I am building a capacitive feedback amplifier whose schematic is shown below. The circuit has two inputs and two outputs (fully-differential). One input is wired to dc ground and the other to an input ...
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### What are important applications of inductors in todays world? [closed]

Are capacitors more important than inductors? I really want a solid grasp of these 2 components so any answer is appreciated! Where are capacitors preferred to inductors ?
0 votes
3 answers
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### What is the purpose of this audio transformer in the circuit?

I was tasked at work to build some boards, which take a 12 V input from a car audio amplifier and output a lower voltage signal for further processing in a soundcard. Schematic: simulate this circuit ...
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1 answer
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### Why did this simple lead-acid battery charger fail?

The following schematic shows the simple circuit of an LED lantern. One day somebody connects it to the mains supply in order to recharge the battery after several months, but hears a loud sound! The ...
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3 votes
1 answer
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2 votes
1 answer
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### What is the right way to model power converter noise? Should it be considered as voltage or current?

This reference models the converter noise as voltage and the filter is an LC filter (from right to left). Another source mentions the converter noise should be considered as current source. Again ...
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12 votes
5 answers
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### Pull up resistor question

Like many others I'm in software so apologies in advance if the question sounds dumb. I watched some videos, read some articles and also read some answers here, such as: Pull-up resistor clarification ...
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2 answers
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### Bandwidth of simple FM transmitter given in schematic?

The following circuit is a basic FM transmitter, which broadcasts for a limited range of about 10 meters. It is tuned by an LC tank circuit, where the capacitor is a trimmer one. I want to know the Q ...
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-1 votes
1 answer
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### Wave shaping circuit with active filter tuned oscillator

Figure: OP amp filter circuit. This is a problem from a book "Microelectronic circuits",7e by Sedra and smith, OUP. The two op amp circuit is called an Antoniou Inductance circuit as it ...
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15 votes
6 answers
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### Current in a circuit is 50% lower than predicted by Kirchhoff's law

I am a math teacher and in my Linear Algebra class we were solving systems of linear equations that come from Kirchhoff's laws. We were trying to use a physical circuit to validate our computations. I ...
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### Calculate the output voltage from following figure if input is 1V [closed]

Figure shows a circuit consisting of an ideal op-amp. If the input voltage is 1 V calculate steady state amplitude of output voltage.
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3 answers
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### Optocoupler not working properly, current in diode

I have got an optocoupler to switch an output between 0V and 3.3V. That output is also inverted with a NOT gate, but for simplicity, we could focus on just Out_Enable1 signal. As far as I understand, ...
4 votes
4 answers
486 views

### How does the speed controller of this cassette tape motor work?

I am new to this area and for my first project I am trying to build a cassette player. I am up to the point of figuring out the speed control of the motor. I have been analyzing this cassette player ...
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### Effective DC Gain of a Chopped Opamp

I am studying a chopper amplifier circuit and have come across the idea of effective dc gain of opamp. The effective dc gain of the opamp due to chopping is the gain at the chopping frequency. Please ...
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1 answer
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### Why is the voltage $V_c$ equal to the voltage source?

As I said in the title why is $V_c = V_{\text{in}} = 12$V? I tried applying Kirchhoff's voltage law (not sure whether I'm allowed), assuming that the current of the circuit moves clockwise I get : \$...
4 votes
9 answers
825 views

### How is an inverting opamp adder circuit able to regulate its feedback?

Consider the typical opamp inverting adder as follows: Why don't resistor Rl and R1 form a resistor divider and impose 2.5V upon inverting node and drive it to saturation. How is opamp's feedback ...
2 votes
2 answers
741 views

### Why are IC and IE different? Aren't the two 1k ohm resistors in series and thus the current through them should be the same?

Honestly I don't understand how this circuit works and that's why I'm thinking that IC and IE should be the same. Note: This problem is copied from Engineering Circuit Analysis Hayt, Kemmerly & ...
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2 answers
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### Is the Thevenin resistance correct ? Also does it matter whether the load is connected in parallel or series?

So i figured out that the voltage was 9 volts by using mesh currents . My Thevenin resistance however came out to be 60/16 or 3.75 ohms . I short circuited the voltage sources and open circuited the ...
0 votes
3 answers
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### How can I find the voltages V1 and V2 of the circuit?

I know I can reduce the resistances and make the problem a lot easier. But my question actually is how can I solve for V1 and V2 using kirchhoff's laws? Because I tried to do it this way but I can't ...
3 votes
1 answer
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### Why is my "common gate amplifier" introducing a zero when it shouldn't be introducing one as per theory?

I am trying to simulate a cascode circuit followed by a source follower in LTSpice and observe its frequency response. I added a 100GH inductor to serve as negative feedback only for DC, i.e., the ...
2 votes
3 answers
270 views

### How can I get the Thevenin equivalent of this circuit?

I need to do this circuit but I can't do it properly, I don't know if I done well the nodes analysis, the answers are Rth= 79.66 ohm and Vth= 5.29 V, thanks for your help.
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2 answers
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### N-MOSFET switching problem in LTspice

In this circuit as per theory it should switch. But it is not switching. Why it is happening.
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1 vote
1 answer
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### How do i modify this circuit so that it gives a dc output of -5V/+5V [closed]

Thats the picture of the diagram And that's the picture of what I have done so I have tried using the LM7805 and the LM7905 but I am getting it wrong
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1 answer
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### Charge on a capacitor in a RC circuit [closed]

I have been given this problem in which one capacitor is initially charged to some voltage and then connected with another uncharged capacitor and resistor as shown in the figure. I am trying to find ...
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2 votes
2 answers
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### Finding Norton current

I am trying to determine the Norton current between the terminals a and b of the network shown below. $Z_1$, $Z_2$, $Z_3$ and $Z_4$ could be resistors, capacitors or inductors. To do so, I ...
1 vote
1 answer
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### In this circuit, why does the 2k ohm resistor have zero voltage and current? It has a path to the battery, so why doesn't any electricity cross it?

simulate this circuit – Schematic created using CircuitLab Why is this happening? Isn't electricity supposed to take all possible paths? Is solving for this circuit's equivalent resistance ...
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1 answer
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### Node voltages with dependent current source

This is the way I set up this problem: v1-v2/5 + v1/5 = 2I0/20 Io/10 + (v2-30)/10 = v1-v2/5 Setting it up that way gives me a v1 of 28.8 and v2 of 7.8, which isn't correct. I'm supposed to be getting -...
3 votes
1 answer
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### How does this amplifier stage work?

I was searching different circuits to produce sinusoidal waves and came across one that seems simple but I do not understand how it works. It has the usual band pass filter (in this case it was a Wien ...
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2 answers
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### How to find the currents and their directions in circuit?

I want to find the currents in blue, and also their directions. I gave it a try and redrew the diagram like this. The arrows next to the currents represent the directions I assumed them to have at ...
0 votes
1 answer
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### Why does this high pass filter/rc differentiator behave like this?

Take a look at this circuit below: If I'm correct, the circuit above is an RC differentiator/high pass filter. However, I do not understand its behavior. The circuit produces an output like so: (...
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2 answers
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### How to find the total equivalent resistance for a circuit? [closed]

RT is the total equivalent resistance. The thing is, can you actually turn the resistances for each circuit into a single equivalent resistance? And how? For c) I see that the two 4 ohm resistances ...
1 vote
1 answer
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### Applying Thevenin theorem on pure resistive ac circuit

This review problem has been stumping me for days (very rusty). My initial approach was hooking up what I believe would be an AC source with $V_p \times \cos(1000 \times 2\pi)$ in series with an Rth ...
1 vote
0 answers
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### Problems with understanding the potential and voltages in circut [closed]

I'm asked to find $V_\text{out}$. The solution suggests to find $V_{C}$ and calculate the voltage on R2 using voltage divider on R1 and R2. My problem is understanding what does it mean finding ...
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1 vote
1 answer
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### Theory of high-voltage spark generators using pulsed transformers

I was looking to build a small electric spark generator and stumbled across this circuit or slight variations of it more or less everywhere I looked: I am not entirely sure of the way it works since ...
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1 answer
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### SCR relaxation oscillator does not oscillate when it should

I am studying this SCR relaxation oscillator and I cannot predict when it oscillates and when it does not. The idea seems simple: as soon as the cathode voltage drops below SCR's gate trigger voltage,...
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1 answer
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### Current limitation in hair electrolysis removal circuit

NOTE: Added by moderator. The voltages and currents when applied as described in this question (no more than 9 VDC) would be considered safe under almost any regulatory system. Higher voltages and ...
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3 answers
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### Behavior of two hypothetical generators in parallel powering the same circuit?

We can't mathematically describe what happens when two generators(simple batteries ) in parallel power the same component with two different voltages, as anomalies arise in the study of this circuit. ...
2 votes
1 answer
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### Voltage Response of Equivalent 1-RC Model for a Lithium Ion Cell

Context: While studying Equivalent Circuit Modelling of Li-Ion cells, I came across a rough approach to approximate the model parameters. My source is this (Refer Book Page 39 in sample) The model is ...
-1 votes
0 answers
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### LTSpice simulation circuit Amplitude doesn't like the real circuit problem

I built the function generator circuit on a breadboard. I applied a signal with an amplitude of 1.06Vpp and a frequency of 5MHz using the DDS 9851 and then sent it to the operational amplifier, AD ...
0 votes
3 answers
80 views

### RL, DC circuit with a resistor in parallel

I've been revising for an upcoming exam and keep coming across this format of question, A coil with internal resistance N, is set in parallel with a resistor M, both in parallel with a voltage source ...
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4 answers
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### Resistance between any two points

I saw a series of simular questions, where was calculated the equivalent resistance of a circuit, but I don't understand a algorithm of calculation for a pair of specific points. I found a solution ...