# 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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### PNP not controlling which LED is on as expected

I have a simulated circuit below, where a PNP determines when LED 1 or LED 2 is on or off. I don't understand why LED 2 is on when the PNP is active and LED 1 doesn't turn on but stays off. Is this ...
36 views

### Input Signal for a voltage amplifier

My question is about the use of the capacitor and resistor for the input signal in the following three-terminal device model used for voltage amplification. The above images show the three-terminal ...
40 views

### Impact of current noise in two "systems"

A section of a nerve cell membrane can be described by an electrical circuit according to the Hodgkin Huxley principle - according to Kirchhoff's law the sum of all currents = 0 and using Ohm's law ...
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### Ideal diode circuit with two AC sources

Consider the following circuit: simulate this circuit – Schematic created using CircuitLab with $V_{1}=100\sin(\omega t)$ [V] and $V_{2}=45\sin(\omega t)$ [V]. Assuming we have an ideal ...
77 views

### RC circuit - R/C ratio meaning

in all the analyses of the RC circuits (direct current) that I have seen, the governing term is R multiplied by C. For example: $$\frac{V_{c}}{V_{in}}(s)=\frac{1}{1+RCs}$$ Obviously, there should be ...
67 views

### Coupling capacitor to receiver antenna

What is the relevance of the left 470pF capacitor coupled to the receiving antenna in this circuit (here the site where I found it):
55 views

### Filters for potentiometer potentially causing issues with ADC

I am sampling potentiometers on an Arduino Zero using the SAMD21 microcontroller. Listed on the SAMD21 datasheet the ADC input is 3.5 kiloohms of impedance. On my setup I am using a low pass filter by ...
331 views

### DC circuit analysis

In the below circuit when I solved in methods A and B the current in the 2 ohms resistor is 3.4 A. However, in method C the current in the 2 ohms resistor is 0.9 A. Where is my mistake?
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### ESP-12E circuit problem

I am trying to use an ESP-12E module to detect a voltage & drive a MOSFET and LED. My schematic is attached. I am having trouble getting this on and after checking it several times, I can't ...
40 views

### Plot a transient analysis over frequency steps [LTSpice / Simetrix]

I am looking for a way to plot the end value of a transient analysis (let's say the output voltages of a SMPS after 3 ms) over a parameter (in this case frequency from 10 kHz to 250 kHz in 10 kHz ...
36 views

### Powering MCU with both battery and USB-C

I am attempting to create something resembling this. I am a total novice so I have some questions. My questions are: I am confused about Battery Protection IC's +5V and BAT+ parts. Is having more ...
53 views

### Impedance matching in Transmitter Circuit

Consider the FM transmitter circuit from here (https://eeeproject.com/fm-transmitter-circuit/) with circuit diagram In this question (Antenna in Transmission & Receiver circuits) I was going to ...
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### NPN and PNP Transistors. Does switching the transistors hard at it bases, how will it affect the transistors?

In my circuits below, I'm using a NPN 2N2222 and PNP MMBT2907A, I implemented this high side switch circuit and it works. However, I'm very concerned about the resistor values that I used. In my first ...
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### Decoding and connetting a keyboard PCB [closed]

I want to build a laptop from a raspberry-pi and an old "toy laptop" (and new components), the spare toy laptop I have is a Oregon Scientific Batman BL31T. I would like to use its case and ...
461 views

### How do we derive the values for these Thévenin equivalent circuits?

I am currently studying the textbook The Art of Electronics, third edition, by Horowitz and Hill. Appendix D Thévenin's Theorem says the following: In Chapter 1 we stated (but did not "prove&...
59 views

### State space model in the form of dx/dt=AX+BU

V=IZg V=IaZ IaZ=IZg LdIc/dt+RIc=(L+Lg)di/dt+(R+Rg)i simulate this circuit – Schematic created using CircuitLab Hi , how can I get state space model in the ...
46 views

### Nodal Analysis Newbie Question

So I was solving some nodal analysis questions for practice and I can't figure out the equation for Node 2 at I2. The voltage at node 1 is V_A and Voltage at node 2 is V_B. A little side note is that ...
33 views

### Gain of a Modified Common Gate Amplifier

I want to know how the gain of the amplifier shown below can be calculated. The gain turns out to be as shown, but why? I know that the gain of a common gate is gmRD, but is the circuit shown here a ...
82 views

### 555 PWM circuit set frequency shifting after 2 months

Please refer to post PWM generator circuit review for initial simulation and bugs on the circuit. In general, the circuit works very well and I can control a 12V fan with the PWM output of the 555 ...
845 views

I am trying to build a guitar pedal but am unfortunately failing. I have about a high school physics understanding of electronic circuits, but the readings I am getting seem impossible to me. I might ...
59 views

### LTSpice: hand calculation vs simulation - GDS/ro value

I've created my own PMOS/NMOS models (LEVEL 1) for test purposes. The DC results match with the theoretical values but there is a mistmatch regarding the output conductance. Here is the testbench: ...
116 views

### Why isn't this multivibrator working?

I've built a simple multivibrator circuit and PCB but I get no oscillation whatsoever. I am expecting an oscillation on pin 3 of each transistor but get 0V on TR2 and 12V on TR1. Can anyone suggest ...
547 views

### Via role in a 6 layers PCB Stack-up configuration

I am using a 6 layers PCB with the stack-up configuration shown below, representing only few components there's in the board. A proposed path to the current is shown to be analysed: QUESTION: When ...
88 views

### New resistance calculation after increasing wattage

I have some small lights in series (similar to the ones for Christmas,) normal ones not LED. They are powered with 3 batteries of 1.5 V and in series there is a resistor of 7.5 ohms (1 W I believe.) I ...
55 views

### How do I get the value of the dependent source in this circuit?

simulate this circuit – Schematic created using CircuitLab I'm very confused, since they are in parallel wouldn't the voltage of $R_1$ be equal to the voltage of $R_2$ and is also equal to ...
165 views

### finding state space equation in x=Ax+Bu form

Can anyone please help me to find the state space equation of this circuit diagram in the form of x=Ax+Bu? The equation I am getting is not giving me square matrix. Can anyone help please? These are ...
55 views

### Termination resistor in RTD analog front end

First of all sorry for my English, it is not my first language and sometimes I cannot make myself completely clear. I am in a project in which I would like to use RTD in order to measure temperature ...
50 views

### How can I follow the current in this DW01A circuit?

I try to understand the inner logic of this diagram, this a modified version of a schematic that I found online. I made the necessary calculations for my power MOSFETs and all but I have some ...
46 views

28 views

### Determine equivalent constant voltage source

As the current drawn from a dc power supply is increased from 600mA to 800mA,the terminal voltage decreases from 24 to 23V.determine the equivalent constant -voltage source. The answer is 27v and 5 ...
35 views

### Finding the contribution of a voltage source

So i am trying to find the contribution of the voltage source in the circuit shown across the 3 ohms resistor. Do I need to include the two 2 ohm resistors even though there is no path that starts at ...
104 views

### Where have I gone wrong with this nodal analysis calculation?

I am a bit confused as to where I have gone wrong in my nodal analysis calculation: For the first node v1: $$-3=(v1-v3)/2 +(v1-v2)$$ v2: $$-(v1-v2)-(v3-v2)/4 = v2/3$$ v3: 7=(v3-v4)/5+(v3-v2)/4+(v3-...
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### What is the output of the integrator? How do I find the frequency? Op-amp integrator+Schmitt trigger

This is the circuit: Integrator analysis: From this formula I don´t know how to get the frequency. (I don't know if this is right, but I think it is.) I found a website that says the frequency is R3/...
1k views

### Does the circuit troubleshooting tool used in 2001 A Space Odyssey exist in the real world?

In the well known science fiction film 2001 A Space Odyssey there is a scene in which Bowman and Poole are trying to locate the fault in the AE-35 unit. If memory serves, they use a tool which allows ...
2k views

### Will the net current drawn by a microcontroller equal the current supplied by it

Purely a theoretical question. Consider a microcontroller whose only job is to turn 1 pin high and in the process the microcontroller supplies I1 current throught the pin. But suppose we have to turn ...
119 views

### NPN and PNP to drive LEDs

I have the following circuit below. One of the restrictions I have is that I need to drive 4 LEDs using 9V. (sorry I forgot why 9V is not enough for all 4 LEDs in series so there's a drop voltage ...
79 views

### What's the performance difference between these two differential amplifiers?

Both of the below circuits are sinking 1A of current.The TL074 has a slew rate of 13V/us and OP07 0.3V/us. Does that makes the upper circuit have s slower response time? What other differences, ...
26 views

### SBC power on LED Indication

I am using SBC ABP 3000 in my application. The SBC will be placed inside a unit. I need to provide the SBC turn on and Off status to the external LED for indication. In the user manual, the J-status ...
94 views

### Inductor behavior in DC circuit

An inductor in a pure DC circuit once steady state is reached has a zero volts across it. In the figure below, the inductor will have a voltage which is not zero Why isn't VL zero?
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### Output enable logic of AM26LS32AID

I am planning to use AM26LS32AID in my design. In order to enable the output pins of this chip, G and #G need to be connected to VCC and GND respectively as per the datasheet. AS per the below logic ...
84 views

### Different voltage sources in parallel (Ideal)

What if we connect two different voltage sources in parallel in ideal condition? From the question here that is assuming internal resistors, Different voltage sources in parallel, I thought I can ...
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### How to explain the simulation results of this op amp from LTspice?

Here is what caused my confusion Why the simulated output voltage is not 0 when the input amplitude at both terminals is 0. When the input amplitude is 0(i.e.the input terminals are short-circuited), ...
103 views

### LED blink circuit with push button

simulate this circuit – Schematic created using CircuitLab I am trying to build a circuit on a breadboard that consists of two LEDs and a push button. Using the button, I would like for the LEDs ...
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### Nodal Analysis - Kirchoffs Current Law

Hello, I am stumbling across an issue here. So in Nodal Analysis, we identify our reference point and label the voltage nodes. Then we use KCL to find out equations and solve. My book is providing an ...
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Hello everyone, I am understanding the concept of mesh analysis and super meshes. In the Practice problem below, I am presented with a dependent current source and it lies between mesh 2 and mesh 3. ...
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### Thevenin equivalent resistance of a complex circuit

I have a complex circuit. I have found the thevenin equivalent voltage V_t, by making two equations. Its V_t=3.877 V Now I have to find the thevenin quivalent resistance. I was thinking of short ...