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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27k views

How do I use superposition to solve a circuit?

Yes, this is a pedagogical question. While answering another recent question, I wanted to refer the OP to concise instructions for using superposition to solve circuits. I found that all the easily ...
45k views

Do electrons actually flow when a voltage is applied?

It's said in books that a circuit is a closed path and thus that electrons come back to the source. If that's the case, what would happen when there were an earth fault in a circuit? How would the ...
43k views

How does the tester screwdriver work?

How does the tester screwdriver work? If I put the tester screwdriver inside the "hot wire" of an electrical socket, it lits up if I press my finger against the metal cap on top of the screwdriver. ...
2k views

Logic level converter using Transistors

I am trying to make a logic level converter using transistor BC547. This is to convert Voltage level of Rpi Gpio from 3.3 to 5V. I have wired the circuit according to this diagram: I have done this ...
53k views

STM32 Understanding GPIO Settings

In STM32 Standard Peripheral library, we need to configure the GPIO. But there are 3 functions which I not sure how to configure them; GPIO_InitStructure.GPIO_Speed GPIO_InitStructure.GPIO_OType ...
8k views

Why can current only flow in loops? [duplicate]

In the following image: Why can't current flow across the following wire? It's a simple question, but I've kind off always wondered. Thanks!
946 views

How does early voltage affect collector current?

The transistor in the following circuit is said to feature $I_{C} = 1.0mA$ at $V_{BE} = 0.7V$ and $V_{CE} = 10V$. If $V_{A} = 50V$ and $\beta = 50$, find $V_{B}$ and $V_{C}$. simulate ...
4k views

Does the resistor have to be before or after the component [duplicate]

I am an electronics beginner and I created a small little circuit, just a battery a resistor and a led, then to ground. This is the circuit: simulate this circuit – Schematic created using ...
238 views

Operation of tuned collector feedback oscillator

I am trying to understand the following tuned collector feedback oscillator extracted from here using LTSpice. I understand that L1 and C1 creates the resonance at the oscillation frequency and L2 ...
367 views

Why is the voltage of a capacitor equal to the voltage of a battery connected it?

I am confused by this question. If we connect a resistor in series to capacitor then the voltage will drop across the resistor and now voltage across the capacitor is less than the source, then why ...
3k views

Meaning of Sigma in Laplace transform

I found the question below in a forum and I also have same problem. Unfortunately, there is no answer at all so I will post it here hope someone could make it clear. A gain relation in a circuit of ...
2k views

How do you determine the effective resistance of a finite grid of resistors?

Disclaimer: I am a geophysicist with limited electrical engineering background. I am not sure if this problem is incredibly easy, incredibly complex, or completely nonsensical. My goal: Determine the ...
3k views

What is AC actually?

What is actually alternating current (AC)? And direct current (DC)? I've been reading several books about basic electric circuits analysis and they are contradictory. Some books say that AC is the ...
833 views

Self Checking Circuit

I was reading the specs. of an electronic module used in process-safety applications & came across this note: Self-Checking (Circuitry): a circuit with the capability to electronically verify ...
719 views

Analysing a circuit to determine what is in series or in parallel

This is probably a very basic question but I have the following circuit, I am not sure what is in series and what is in parallel or if they are all in parallel, initially I thought R2 and R3 were in ...
129 views

Why is D2 switched off and T4 not in saturation mode in 7408 TTL Gate as shown below?

In the circuit, when both the inputs are high at 5V, than why is D2 switched off? Will it not draw voltage from Vcc? Also, when one of the input is low, why is T4 not running in saturation mode? Will ...
7k views

What is a flip flop?

There seem to be a number of different definitions of flip-flops and latches out there, some of which are contradictory. The Computer Science text book for the course I teach is probably the most ...
7k views

How does this timer circuit work?

I am stumped on how this circuit works. I am quite new to electronics but I know the basics of capacitors, transistors, ohm's law .etc, but I have no clue why when the switch(S1) is switched on the ...
25k views

Superposition principle: Dependent sources treated as independent sources

Since I began studying, I was taught that when analysing a circuit using multiple sources, independent sources could be turned off, meaning that I could transform a voltage source into a short, and a ...
3k views

Why superposition theorem fails here?

I have a simple circuit consisting of 2 ideal voltages sources (each 5V) parallel to a resistor of 5 ohms. The current along the resistor is 1A, right? But by applying the superposition principle (i.e....
557 views

How does a Miller cap physically create a pole in circuits?

If we consider a single NMOS transistor (with its source terminal grounded) and a Miller cap (C) between its input (gate) and output (drain) nodes, circuit theory says that this Miller cap will be ...
117 views

How can i transfer 12 V, 50 Hz, 1 A wirelessly? [closed]

I want to transfer electical power wirelessly from a transmitter to a receiver coil. Input energy is provided by a single phase step-down transformer - 230V/12V AC, 50 Hz, 1,000 mA. Using the 12 V ...
5k views

What is the most economical way to drive an array of single coil latching relays?

Please read the question to the end. The answer to this question may be non-trivial. Replacing a number of 2-coil latching relays with single coil latching relays ...
919 views

Calculation of output impedance of CE emitter bias configuration( unbypassed) with r_0

Can anyone please help me with finding the output impedance of the circuit.? I tried but can't find the answer
3k views

Why is the voltage across the inputs of an ideal OP Amp zero?

The property that the voltage across the inputs of an ideal OP Amp is zero cannot be taken as an axiom because it isn't a property you can directly "adjust" (as opposed to say the resistance across ...
470 views

Help understanding how op amps work

I've just been introduced to op-amps and am having a little trouble understanding exactly how they work. Take this circuit, for example. Suppose that there's a 1V source here. Without the op amp ...
2k views

How to interpret Vgs(th) min/max in a MOSFET datasheet?

This is a screenshot of IRF9640 MOSFET datasheet. Will you please tell me, what is meant by max and min value of Vgs threshold voltage. Also what they mean by test condition. Whether the max and min ...
89 views

Norton equivalent with a single voltage source

I'm trying to find the Norton equivalent with respect to the load resistor RL for the DC circuit below. Each of the resistors have an equal resistance R. Removing the load resistor, I am having a ...
8k views

How does a capacitor function in a 120v ac motor circuit?

I dont understand the direction of current flow when a capacitor is wired in series with the start windings in, say, a fridge or ac motor running on der 120v ac. Wiring diagrams seem to suggest ...
2k views

Find total resistance of this circuit

I want to find the total resistance between A and B. This is a HOTS mcq, which has the following options: A: 45$\Omega$ B: 15$\Omega$ C: 5$\Omega$ D: 22.5$\Omega$ A book says that the answer ...
416 views

Is this an astable multivibrator?

In this circuit the LED flashes on and off, however could it be classified as an astable multivibrator?
826 views

Intuition behind why nodal and mesh analysis work?

I'm looking for an intuitive explanation (not a proof) of why the equations produced by nodal analysis and mesh analysis are always linearly independent and always have a unique solution, if the ...
108 views

Is there current flowing through this blank wire?

simulate this circuit – Schematic created using CircuitLab Does any current flow from point A to point B? My guess is no. Because both of those points are connected to a ground symbol by ...
877 views

Calculation of Steady state power limit

I am confused with the above problem. I was thinking shouldn't we maximise $\mid E\mid sin(\delta)$ instead to get steady state power limit? $\mid E\mid sin(\delta) = 1.8 sin(\theta)$ maximum ...
3k views

Counter with 4 flip flops jk synchronous from 3 to 13!

I have to create a counter with 4 flip flops jk synchronous. The counter shall count in this order: 3 to 13 and then to 3 to 13 and so on.. I have to use logisim simulator. Ok. So i think its ...
12k views

How do Circuit Simulators actually work?

I recently had the opportunity to play around with LiveWire, which is a circuit simulator and began wondering how exactly they computed the voltages across each component and the current going through ...
2k views

Under what conditions is the star-mesh transform invertible?

We all know and love the Δ-Y (delta-wye) and Y-Δ (wye-delta) transforms for simplifying three-resistor networks: Image from Creative Commons The Δ-Y and Y-Δ transforms have the nice property that a ...
1k views

Electrons of the current in a circuit?

I have a traditional circuit (a conductor wire, and voltage source and a resistor). The voltage source may be a battery in this case. My questions(s) are: From where do the electrons that flow in ...
7k views

Zener Noise Generator - NPN BJT Amplifier Analysis

I'm interested in creating a low voltage white noise generator by means of a zener diode, as detailed here: Zener & BJT Noise Generator. Specifically, I want to use the circuit here, in order to ...
3k views

OP Amp with T network feedback

Hello i want to know how to calculate the equivalent T network resistors in the inverting amplifier below (the answer is 10M but i dont know how) ,i dont need formula but indepth circuit analysis ,...
3k views

Why, in a passive circuit with a sinusoidal input, do all voltages and currents have the same sinusoidal behavior as the input?

I am familiar that in any circuit composed of linear passive elements and a sinusoidal input, all voltages and currents through and across any element will exhibit the same sinusoidal behavior and ...
1k views

Application of Complex Numbers [closed]

I was just wondering how complex numbers can be applied in electrical engineering and why we use complex numbers over regular, real numbers for this application (e.g what capabilities does the complex ...
4k views

A 1USD 11W led bulb circuit and parts analysis

I know this is not a huge deal, but still I want to do it because for Three reasons: 1, it only costs 1 usd. Yep, this is a very cheap led bulb, and I need to take it apart to see if it's trust worthy....
3k views

How do I achieve XY mode on LTspice?

I have two node voltages that I wish to plot against each other, similar to the XY mode on an oscilloscope. How do I achieve this via LTspice? LTspice only plots quantities against time.
1k views

Solving an Op-amp circuit

The image of the circuit is shown below and it required to find $V_0$, My first attempt at solving this problem is by changing the current source into a voltage source with 1-V and 2k$\Omega$ ...
371 views

Analyze a circuit with two diodes and two voltage rails

I want to find $I$, $I_{D2}$ and $V$ in this circuit. The diodes are made of Silicium. I'm a beginner and normally I would assume the Diode bias and then apply KVL to see if it is true. However, ...
463 views

Why does DMM show AC and DC current when source is a battery? (How to calculate power in this case?)

The circuit is an altered Joule Thief of my design that is driven by an AA or AAA battery. I’m observing the current at the battery anode with my DMM in series. (Extech EX330) This circuit is ...
531 views

Understanding this AC coupled circuit

I'm having a little trouble understanding this circuit and could use some help. So far I understand that this is an AC coupled circuit, and the capacitor is a blocking capacitor. I also know that ...