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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Help with supercapacitor charging circuit

I need to design a circuit to charge a capacitor from 0 to 2V. The circuit should not be that complicated and no matter the type of capacitor, it should never exceed 2.7 V when charging. The capacitor ...
2 votes
2 answers
57 views

Transistor in saturation mode conditions

I have this circuit where the voltage \$V_A = -4.6V\$ is imposed. I made the hypothesis that the transistor is saturated. Then I calculated \$i_B\$ through KVL: $$-2 + R_Ci_E + V_{EBon} + R_Bi_B + V_A ...
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6 votes
5 answers
758 views

Transistor working region hypothesis

In the following circuit of a transistor I know that \$V_A = 2.5V\$. How do I know in which zone the transistor is operating? As I understand it, I should make an hypothesis into one of the working ...
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2 votes
2 answers
165 views

Supply-independent current source

In the given circuit, the resistor defines the current and it is connected at the source of M2 in this circuit. What will happen if it is connected to the source of M1? I don't see any problem, but I ...
0 votes
2 answers
48 views

Thevenin from terminals point of view in transistor circuit

I know (from the textbook) the Thévenin expressions for the circuit from reference terminals b-b' are $$V_{th} = V_{CC}\frac{R_2}{R_2+R_1}, R_{th} = R_1//R_2$$ But ...
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2 votes
2 answers
92 views

Why is this not a negative half wave rectifier? What is it?

In the AC circuit below with \$V_{IN} = 20\sin(\omega t)\$ and \$\omega=1\pi\$, we have an ideal diode (inverted) and a capacitor in parallel with a resistor. I want to study the voltage across the ...
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2 votes
2 answers
73 views

Imposing voltage

I have two questions from the circuit below, with an ideal diode and \$v_1(t) = 20\sin(\omega t)\$: If \$V_2 = +5\ V\$ I guess the diode would be ON (because \$V_2 = u_D\geq 0\$). In that case, would ...
  • 525
1 vote
2 answers
47 views

Guitar distortion pedal gain

I am working on a custom distortion pedal. Here is the circuit: As we can see, we have the following flow: Input buffer -> gain stage with hard clipping -> buffer -> tone control using ...
0 votes
5 answers
101 views

Could someone explain why reactive components like the inductor and capacitor are needed in circuit? Can't they be avoided? [closed]

I just don't get why they the inductor can't be avoided. It's this same Device that causes reactive power. Could someone explain why reactive components like the inductor and capacitor are needed in ...
5 votes
2 answers
95 views

Why is the output voltage expression wrong?

I derived the expression for the output voltage in this circuit, however, I have got the wrong answer. The problem is that I just know that it is the wrong answer because it's a multiple choice ...
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-1 votes
1 answer
69 views

Simplification of a capacitor circuit with nodes

If the problem is something like : Capacitors of 2 Farads are connected between pair of nodes (a,c),(c,d),(a,d),(b,d),(c,b) and we have to find equivalent capacitance between node a and b. Which can ...
7 votes
6 answers
2k views

How to know if this is a band-pass filter?

I have the circuit below. How can I see that it is a band-pass filter? I tried calculating the equivalent impedance for the parallel part of the circuit: $$\bar{Z}_{parallel} = \frac{\bar{Z}_C\bar{Z}...
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1 vote
1 answer
43 views

MOSFET circuit analysis gate drain shorted resistor from source to ground

I need to find the voltage across the 1k resistor in the below circuit. My approach is given below. I would like to know if the way I am approaching this problem is correct or not. The gate and drain ...
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2 votes
1 answer
115 views

Phasor calculation doubles frequency?

When working with phasors we have $$\bar{Z} = A\cos(\omega t + \phi) = Re(Ae^{j(\omega t + \phi)}) = Re(Ae^{j\phi}e^{j\omega t})$$ where $$\bar{P}_1 = Ae^{j\phi}$$ is the phasor. But when we multiply ...
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2 votes
0 answers
49 views

Diode conduction angle for inductive and capacitive load [closed]

I need to calculate the conduction angle of the below circuit in two cases: A 1 μH inductor as load as shown in the figure; The inductor is replaced by a 1 μF capacitor. My source is a 10 V peak ...
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6 votes
0 answers
163 views

What textbook is this problem from? (circuit analysis)

A somewhat unusual question: Some years ago, the following problem appeared in a test I took during my Bachelor's in electrical engineering. Later, the professor told us which textbook he took it from,...
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4 votes
1 answer
65 views

How to calculate expected RMS noise voltage out of digital audio system?

I have a PCB which includes an SOC with a built-in DAC that connects to an external active high-pass filter which then connects to a Class AB amp IC to drive an audio load. Using a spectrum analyzer, ...
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1 vote
0 answers
38 views

How do I construct my circuit with inputs connected to battery return?

I am trying to simulate my circuit and I need my inputs connected to my power supplies's returns or the negative terminal but now I am confused on what I would connect to the positive terminal and ...
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1 vote
4 answers
116 views

Voltage measured by voltage meter

I am given the following circuit and told to calculate the voltage measured by the voltage meter: My first thought was to calculate the voltage through \$R_k\$ (at the red dot) and the voltage ...
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2 votes
2 answers
113 views

OR MOSFET circuit with considerable current consumption

I'm using the MOSFET circuit presented below to switch the power supply in the PCB (low power). The problem is the current consumption during the ON state of P1, which is 0.5mA to keep-on the pmos (...
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0 votes
2 answers
72 views

Thévenin resistance with simple dependent current source

I want to find the Thévenin resistance from the terminals a-b. I've been trying out various methods that look correct to me but none of them seem to be the right answer: 4/9 kΩ. First, according to <...
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0 votes
1 answer
79 views

Current sense circuit: small current

I simulated a current sensing circuit below. I understand Ohm's law and how I have 476 mA throughout my circuit. What I do not understand is how I have such small current values going into R2 and R3 ...
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2 votes
1 answer
45 views

Mesh Method with current source

I found an exercise with the circuit below and for which I'm asked to use Mesh Method for every essencial mesh (explicitly the loops I1, I2, I3) in order to find the equations that allow me to solve ...
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-1 votes
1 answer
68 views

Current, voltage, and power interpretation

I have been working with circuits a lot more lately and not just modeling them. I think I never had a good enough understanding of the fundamental theory of voltage, power, and current. Voltage is ...
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0 votes
1 answer
77 views

Branch current method for a given circuit

Could somebody check if I did the branch current method correctly on the given circuit immediately after the switch has been closed? See the circuit in Figure 1.1 in the image below. My solution ...
1 vote
3 answers
76 views

Current monitor/sense circuit

Has anyone ever dealt with a circuit similar to the one I have? It is a current sensing circuit but I do not understand how it works. I believe there will be a voltage difference between my R2 and R3; ...
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0 votes
1 answer
48 views

Verifying answers for current through each resistor question

I found this question and would like to know whether my solution is correct. I need to work out the current through each one of these resistors. I got the following values for the current: I1 = 8.75 ...
0 votes
1 answer
91 views

How can I power a 5 V - 7 V buzzer with a 24 V power supply?

I'm working with a 24 V power supply. I know I could use a voltage regulator to 5 V to power the buzzer (see image below), but I wanted to experiment to see if could make it work with just a resistor ...
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2 votes
2 answers
70 views

Common-collector gain for guitar pedal

I am currently working on a distortion pedal. I have just made the initial input buffer to prevent loading the source signal. It is simply an NPN transistor in an emitter follower (common collector) ...
0 votes
1 answer
79 views

How do you find the inductance in this AC circuit?

So far I can think of only one equation for a) So XL=2.(3.14)fL Then rearrange L=2.(3.14).50.XL If I know L then I can do the rest of this problem
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5 votes
2 answers
496 views

Why is the potential difference and EMF not the same?

If EMF and the potential difference have a unit of volts, why are they different from each other?
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0 votes
1 answer
37 views

De-normalizing capacitor and inductor values when resistances are different

I need to know when we de-normalize capacitor and inductor values when the source resistance and load resistance are not equal to each other. How to de-normalize the inductor or capacitor? The ...
1 vote
1 answer
54 views

Differential amplifier with ideal current source and resistive loads

In this circuit, I want to find how each node's voltage changes as Vin changes. My approach is as follows: The total current is 2·I. The current in R is fixed and equal to I which implies that Vo2 is ...
0 votes
2 answers
82 views

Why does current source define the current to all loop?

Lets say I have this circuit below and I want to solve it using the Mesh Method. For every essential loop I define the current loops \$i_a\$ (left), \$i_b\$ (right), and \$i_c\$ (below) clockwise. ...
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3 votes
4 answers
266 views

Question on circuits with current sources

I'm having trouble understanding some concepts in simple electrical circuits and I was hoping to clarify it because it has been the my source (pun intended) of wrong answers. Lets say I have this ...
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0 votes
2 answers
108 views

What does "CC" mean when it is labelling a capacitor?

I'm looking at a circuit diagram that doesn't list the capacitance for a couple of capacitors. There's "C1", "C2" and "CC". I can't imagine "CC" meaning ...
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-2 votes
3 answers
67 views

How can I calculate what voltage I have in the middle of 2 series resistors in an electrical circuit?

For example: VCC 5 V - resistor 1.5 kΩ - resistor 860 Ω - GND
0 votes
1 answer
119 views

Speed control of a PSC induction motor, how does it actually work?

I'm trying to understand the physics and engineering behind speed control on PSC induction motors, usually seen in fans/HVACs. I have come across this link, but I don't quite understand everything ...
0 votes
1 answer
67 views

Why is the voltage negative in this circuit?

I was trying some simulations and tried the below circuit. My question is, how is the below marked voltage negative (-3 V)? I thought like, since there is a diode, there will be approximately 4.3 V ...
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0 votes
2 answers
88 views

Method for always getting the sign of the power right

In a circuit setup like the one below, I'm asked to find the power at the voltage source. I did: $$KCL: I_V + I = I_R \iff I = I_R-I_V$$ $$I_R = \frac{V}{R} = \frac{1}{200} = 0.005 A$$ $$P_V = VI_V = ...
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3 votes
2 answers
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Fermi level of metal

Do metals have fermi level? As we know conduction band and valence band are overlaped for a metal. Does it make any sense for metals to have fermi level?
1 vote
1 answer
122 views

Understanding inductor behaviour in a diode circuit

I am trying to understand how this circuit works without burning or exploding. When the inductor current starts to decrease, it acts in a way to increase it and if there is no path, then we see sparks ...
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2 votes
3 answers
384 views

Differential pair with active load including resistance

In solving the differential pair with an active load, I am able to find the gain without including R1 as shown in the figure. When R1 is included, I am stuck on how to proceed. Could you help me out? ...
0 votes
1 answer
45 views

How to throttle / load balance between utility and battery power supply

Basic queation - What kind of circuit allows me to throttle the power draw from two different supplies? i.e. 80/20 from a battery bank and utility power, respectively? Or 60/40, or 100/0? Main idea - ...
2 votes
1 answer
91 views

Question on INA122P non-linear gain

I am trying to apply gain for a 0.0 - 16.7 mV signal with an INA122P, with a single 10 V supply for all the circuits, with Vref driven at 0.0 mV. Here is the circuit that I am using, no Rg applied, ...
0 votes
0 answers
28 views

Erroneous oscillation voltage for LC Tank in Cadence Virtuoso

I simulated an LC tank with an ideal inductor and capacitor. The inductor's initial condition was 0 and the capacitor's was 300 mV. I expected it to oscillate with an amplitude of 300 mV, but it ...
0 votes
1 answer
51 views

How do I derive the equation for current as a function of time \$I(t)\$ through resistor in this CLCR circuit schematic with a sine wave AC source? [duplicate]

How do I derive \$I(t)\$ through the resistor for the circuit schematic below? What method should be used. So far, I have tried mesh analysis for the 3 meshes using KVL but the system of equations ...
0 votes
0 answers
132 views

cross coupled nmos pair

For the given circuit, I am observing the source voltage of M1 and M2 as the min of the applied voltage. Here, the current is equal in both fets. But Vg is not the same. So, both cannot be in ...
5 votes
1 answer
75 views

Instrumentation amplifier cross-connection circuit

I am trying to implement a circuit from an ADI app note that I have not seen anywhere else : Here it is in PDF format which is a copy of this article. I strongly encourage reading it as it is quite ...
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1 vote
1 answer
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Is the "\$\small o\$" in \$r_o\$ short for output or number 0?

You usually see ro in the small-signal models of BJTs or MOSFETs like this. I'm curious if the "o" there is short for "output" or just the number zero? I think I saw people reading ...