J.W.L. Jan Eerland
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Are the 3 resistors in parallel or in series?
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10 votes

Well, \$\text{R}_3\$, \$\text{R}_4\$, \$\text{R}_5\$ and \$\text{R}_6\$ are in parallel and they are in series with \$\text{R}_1\$ and \$\text{R}_2\$. simulate this circuit – Schematic created ...

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How do you calculate power loss for a diode?
9 votes

Well, let's make a mathematical closed solution. I know that this is maybe above the OP's knowledge, but I think it is important to show it in combination with the other answers given. We know that ...

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How to calculate susceptance of an inductor in series with a resistor
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7 votes

Well, the definition of susceptance is the following: $$\text{susceptance}=\Im\left(\text{admittance}\right)=\Im\left(\frac{1}{\text{impedance}}\right)\tag1$$ In formula form: $$\text{B}=\Im\left(\...

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How is the slope of the frequency response of an analog active filter defined?
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7 votes

Well, generally we have two things that we look at: dB/decade: $$\lim_{\omega\to\infty}\left(20\log_{10}\left|\underline{\mathscr{H}}\left(10\omega\text{j}\right)\right|-20\log_{10}\left|\underline{\...

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High pass filter - Cut-off frequency calculation doesn't match simulation
5 votes

Well, mathematically speaking we can write: $$\mathcal{H}\left(\text{s}\right)=\frac{\text{sL}}{\text{sL}+\text{R}}\tag1$$ Using \$\text{s}=\text{j}\omega\$, we get: $$\left|\underline{\mathcal{H}}\...

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Operational Amplifier with mixed feedback
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5 votes

First of all, you wrote: "defined by the current across" but the current is trough a component, voltage is across. Well, we are trying to analyze the following circuit: simulate this circuit – ...

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Transfer function in ideal op-amp
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4 votes

Well, using the voltage divider formula we can see that: $$\text{v}_+\left(\text{s}\right)=\frac{\text{R}}{\text{R}+\frac{1}{\text{sC}}}\cdot\text{v}_\text{in}\left(\text{s}\right)\tag1$$ $$\text{v}_-...

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Euler's relation and the energy of a complex exponential signal
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4 votes

Notice, that \$\forall x\in\mathbb{R}\$: $$\left|\exp\left(xi\right)\right|=1\tag1$$ Because: $$\left|\exp\left(xi\right)\right|=\left|\cos\left(x\right)+\sin\left(x\right)i\right|=\sqrt{\underbrace{\...

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Finding load current in a circuit with voltage dependent voltage source
4 votes

Well, we are trying to analyze the following circuit: simulate this circuit – Schematic created using CircuitLab When we use and apply KCL, we can write the following set of equations: $$\text{...

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How to calculate phase shift of a low-pass filter's output?
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4 votes

Well, we know that: $$\mathcal{H}\left(\text{s}\right):=\frac{\text{V}_\text{out}\left(\text{s}\right)}{\text{V}_\text{in}\left(\text{s}\right)}=\frac{\frac{1}{\text{sC}}}{\frac{1}{\text{sC}}+\text{R}...

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Instantaneous Current (Inrush) Calculation
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3 votes

Well, we are trying to analyze the following circuit: simulate this circuit – Schematic created using CircuitLab When we use and apply KCL, we can write the following set of equations: $$\text{...

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Current flowing through a Capacitor
3 votes

The voltage-current relation in a capacitor in the time domain is given by the following formula: $$\text{I}\left(t\right)=\text{C}\cdot\frac{\partial\text{V}\left(t\right)}{\partial t}\tag1$$ So, ...

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How does this opamp phase shifter produce 2x phase shift at the output without changing the magnitude?
3 votes

Well, we are trying to analyze the following circuit (assuming an ideal opamp): simulate this circuit – Schematic created using CircuitLab When we use and apply KCL, we can write the following ...

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RC circuit resistor power dissipation
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3 votes

Well, according to Ohm's law we know that: $$\text{V}_\text{R}\left(t\right)=\text{I}_\text{R}\left(t\right)\cdot\text{R}\tag1$$ And the power in a resistor is given by: $$\text{P}_\text{R}\left(t\...

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Circuit analysis with an LED and a voltage divider
3 votes

Well, let's make a mathematical closed solution. I know that this is maybe above the OP's knowledge, but I think it is important to show it in combination with the other answers given. The Shockley ...

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What is the impedance for this parallel rl circuit?
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3 votes

Well, the impedance of your circuit is given by: $$\underline{\text{Z}}_{\space\text{in}}=\frac{\text{R}\cdot\text{j}\omega\text{L}}{\text{R}+\text{j}\omega\text{L}}=\frac{\text{R}\cdot\text{j}\omega\...

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Voltage and current during the first cycle of RL circuit
3 votes

Well, using Laplace transform we can see that: $$\text{I}_\text{in}\left(t\right)=\mathscr{L}_\text{s}^{-1}\left[\frac{\hat{\text{u}}\omega}{\text{s}^2+\omega^2}\cdot\frac{1}{\text{R}+\text{sL}}\right]...

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Calculating maximum power transfer for given circuit
3 votes

First, I will present a method that uses Mathematica to solve this problem. When I was studying this stuff I used the method all the time (without using Mathematica of course). Besides that the answer ...

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Calculate output impedance of emitter follower
3 votes

Well, we have the following circuit: simulate this circuit – Schematic created using CircuitLab When analyzing a transistor we need to use the following relations: $$\text{I}_\text{E}=\text{I}...

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Feedback resistor value in op amp integrator
3 votes

Well, let's solve and show this mathematically. We are trying to analyze the following circuit (assuming an ideal opamp): simulate this circuit – Schematic created using CircuitLab When we use ...

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Simple transistor resistor amplifier circuit question
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3 votes

Well, we have the following circuit: simulate this circuit – Schematic created using CircuitLab When analyzing a transistor we need to use the following relations: $$\text{I}_\text{E}=\text{I}...

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Analyzing a simple circuit with transistor
3 votes

Well, we have the following circuit: simulate this circuit – Schematic created using CircuitLab When analyzing a transistor we need to use the following relations: $$\text{I}_\text{E}=\text{I}...

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How to Calculate Voltage across R2 for any Value of R1, R2, and Frequency?
Accepted answer
2 votes

Well, if we are not looking for the transient behavior of the circuit we can use the complex method to find the answer. First, we can find the current trough \$\text{R}_2\$ using the current divider ...

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Understanding Euler's formula in different forms
2 votes

Your third equation is only correct, if and only if \$\sigma=0\$. Well, when we state Euler's formula \$\forall\space x\in\mathbb{R}\$: $$\exp\left(x\text{j}\right)=\cos\left(x\right)+\text{j}\sin\...

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Signals and systems - Find the inverse Fourier transform of a RLC circuit
2 votes

Well, the transfer function of the circuit is given by: $$\mathscr{H}\left(\text{s}\right):=\frac{\text{V}_\text{o}\left(\text{s}\right)}{\text{V}_\text{i}\left(\text{s}\right)}=\frac{\frac{1}{\text{...

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How to solve this oscillator problem
Accepted answer
2 votes

Well, the current supplied by the source is given by: $$\text{i}_\text{i}\left(t\right)=\mathscr{L}_\text{s}^{-1}\left[\frac{\hat{\text{u}}}{\text{s}}\cdot\frac{1}{\text{R}+\left(\text{sL}\space\text{|...

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Why does the capacitor connection reduce into 110 V instead of 99 V?
2 votes

Well, when we have the following circuit: simulate this circuit – Schematic created using CircuitLab It is not hard to see that: $$\underline{\text{V}}_{\space\text{out}}=\frac{\text{R}\text{||}...

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Phase shift in an active RC shifter
2 votes

First, I will present a method that uses Mathematica to solve this problem. When I was studying this stuff I used the method all the time (without using Mathematica of course). Well, we are trying to ...

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Phasor angle calculation
Accepted answer
2 votes

Well, the angle of the output voltage can be found using the voltage divider formula: $$\varphi=\arg\left(\frac{4\text{||}\left(-2\text{j}\right)}{2+12\text{j}+\left(4\text{||}\left(-2\text{j}\right)\...

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Identifying a multiple feedback op-amp circuit
2 votes

First, I will present a method that uses Mathematica to solve this problem. When I was studying this stuff I used the method all the time (without using Mathematica of course). Well, we are trying to ...

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