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28 votes

Why exactly does maximum power transfer happen at 50 ohms (matched impedance)?

The power delivered to the load is from the Joule heating effect: \begin{equation} P=\dfrac{\Big(\dfrac{R_L}{R_L + 50}G\,V_{IN}\Big)^{2}}{R_L} \end{equation} So from differential calculus we know ...
Iron Maiden's user avatar
  • 1,214
25 votes
Accepted

Will this circuit work ? 100 Leds project

No, that's a really bad circuit. You have 100 LEDs, all in parallel. Bad idea. Since this is a assignment, I'm not going to give you a better circuit outright. However, consider that LEDs want to ...
Olin Lathrop's user avatar
20 votes
Accepted

check if an unsigned binary number is divisible by 15

Do you know how to check for divisibility by 9 in base 10? Add all the digits using base 10 arithmetic. If the result has multiple digits, repeat the process. Stop when you have one digit. If the ...
Neil_UK's user avatar
  • 169k
17 votes

Why exactly does maximum power transfer happen at 50 ohms (matched impedance)?

Intuitively: when you raise the load resistance, you are increasing its share of the voltage (and thus power) versus the other resistance; but you are decreasing the total current (and thus power). ...
Glenn Willen's user avatar
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13 votes
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Inverting op-amp problem

Your simulation won't work unless you connect the op-amp's power supply voltage sources to ground on the other side! Also, the source of negative supply will need to be non-zero. Besides that, another ...
Simon Fitch's user avatar
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12 votes

Combining resistors in a simple network

The ground node has got you confused. How much current flows in the ground? Why treat R4 and R5 different to R1 R2 R3?
tomnexus's user avatar
  • 7,824
12 votes

Trouble understanding when voltages get split

Just re-draw the schematic, slightly: simulate this circuit – Schematic created using CircuitLab (Note that your confusion about "Would the 9V be split between these two resistors?" completely ...
jonk's user avatar
  • 78.3k
12 votes

How can I calculate the current flowing through this diode?

but I'm just not good at solving diodes in parallel circuits So, in general for problems like this (which you do hit in real life if you're doing circuit design, so it's not just academic), you start ...
TimWescott's user avatar
  • 46.6k
12 votes

Problem with equivalent resistance

simulate this circuit – Schematic created using CircuitLab Here's the circuit redrawn. R1 and R2 form a voltage divider, as do R3 and R4. Since the ratios are the same for each voltage divider,...
vir's user avatar
  • 20.3k
12 votes
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How to calculate current at one circuit node in a textbook exercise

Maybe a little visual drawing will help. You can easily calculate the currents in each resistor using Ohms Law. Then using Kirchhoff's current law, all the currents in a node must sum to 0. Note: The ...
Aaron's user avatar
  • 8,061
11 votes
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Calculate total harmonic distortion

The amplitude distortion plot you showed is in dB, dBV specifically (dB's relative to 1 V). So you need to take those dB values and covert them into volts before putting them into your formula. For ...
SteveSh's user avatar
  • 10.9k
10 votes

Design a 8 - 6 - 4 - 2 - 0 - 1 - 3 - 5 - 7 - 9... Counter

Given it is an assignment, I'm not going to work through the logic. However in all such questions you can boil it down to a circuit with two steps: You have a binary ...
Tom Carpenter's user avatar
10 votes
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how to solve this op-amp circuit?

Your circuit doesn't have negative feedback: - Therefore it acts as a comparator with hysteresis and hence, the output changes state when the input voltage passes the hysteresis threshold points ...
Andy aka's user avatar
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10 votes
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Circuit analysis homework - LTspice results are different from calculations

Check your complex arithmetic:- @100Hz I get Za = 4.7000e+03 + 6.2832e+01i Zb = 2.2000e+03 - 3.3863e+04i Zc = 1.0000e+03 - 1.5915e+05i Zp = Za || Zb = 4.5887e+03 - 5.6789e+02i Vo = 4 * Zp/(Zp + Zc) = ...
Spehro Pefhany's user avatar
9 votes
Accepted

Input and Output Impedance parameters of two port network

For the input impedance, expand the matrix equation and then use the output condition: \$Z_L=-\large \frac{V_2}{I_2}\$ Similar approach for the output impedance.
Chu's user avatar
  • 7,646
8 votes

Am I on the right path to solve this RLC-Circuit? (Need to find the voltage at the resistor)

Yes, your analysis is correct. It would have been quicker to solve for the resistor current and then multiply through by \$\small R\$ to get the resistor voltage, \$v_R\$, as below (I've used \$\...
Chu's user avatar
  • 7,646
8 votes

How can I calculate the current flowing through this diode?

You should really simplify stuff before launching into the math. For instance: - Can you see how much easier this is to simplify following the standard source transformation I did above? Do you know ...
Andy aka's user avatar
  • 465k
7 votes
Accepted

Design a 8 - 6 - 4 - 2 - 0 - 1 - 3 - 5 - 7 - 9... Counter

It sounds like you are expected to solve this with a state-machine type circuit, however it can also be done using a classical counter circuit. The key to this problem is recognizing that for half ...
Trevor_G's user avatar
  • 46.8k
7 votes

Am I on the right path to solve this RLC-Circuit? (Need to find the voltage at the resistor)

As you could figure out, your source is expressed as a phasor, hence we can assume safely the solution can be expressed with phasors and impedances, in consistency with the requirement of ignoring ...
Brethlosze's user avatar
  • 1,427
7 votes

Diode stack circuit

Perhaps the easiest way to see is to re-draw the schematic. If there is one thing I try to do, over and over again, it is hammer at this with everyone I reach out to. I recommend early and continual ...
jonk's user avatar
  • 78.3k
7 votes

Design a class AB audio amplifier

For 10 watts into 8 ohm speaker, you can do this system design P = Vrms * Vrms / Rload 10 watts = V * V / 8 10 * 8 = V * V thus Vrms_out ~~ 9 volts RMS, or 2.828 * 9 peakPead You will need ...
analogsystemsrf's user avatar
7 votes
Accepted

Transfer function of an RLC filter

Your numerator in this: $$ v_{o}=v_{oi}\frac{R}{Ls+R_{L}+\frac{R(\frac{1}{Cs})}{R+\frac{1}{Cs}}} $$ Should be \$Z_R || Z_C\$. That is, $$ v_{o}=v_{oi}\frac{R || Z_C}{Z_L+R_{L}+(R||Z_C)} $$
ErikR's user avatar
  • 5,017
6 votes

Effects of using voltmeter w/ 20 kΩ impedance across 35 kΩ resistor?

Instead of claiming you can't do this, stop and actually think about it. Draw the schematic of the circuit without the voltmeter. Then draw the schematic with the voltmeter. To the circuit, the ...
Olin Lathrop's user avatar
6 votes

Finding the current in a parallel circuit

Start by labelling your circuit. You should know that in a series circuit, the current is the same at any point in the circuit. simulate this circuit – Schematic created using CircuitLab We ...
MCG's user avatar
  • 12k
6 votes
Accepted

Calculate peak input current of switch mode power supply

First thing to notice is that you have a a very small output capacitor, which is used to supply the load during the on phase (when the inductor is being charged and there is no power transfer between ...
vtolentino's user avatar
  • 3,589
6 votes

I can’t seem to understand the preference of the flyback converters for the reason given below

When you talk about the differences between a flyback and or forward converter, you could say the following: the flyback converter is usually suited for low to moderate output power (100-150 W as a ...
Verbal Kint's user avatar
  • 22.7k
6 votes

Current across a diode?

You are asked to find the operating point such that the small-signal resistance is 5 ohms, i.e. $$\frac{dv_d}{di_d} = 5\,[\Omega]$$ You can obtain this by both sides of the given equation relating ...
nanofarad's user avatar
  • 20.2k
6 votes
Accepted

Strange Nodal Analysis

Your mistake is again the current direction. For \$V_1\$ node you have wrote: $$+12A + \frac{V_1 - V_2}{2\Omega}....= 0$$ As we can see from a circuit diagram the \$12A\$ current is entering the node(...
G36's user avatar
  • 15.1k
6 votes

Transfer function of an RLC filter

These are the kinds of questions that should be brought here more often. I see that ErikR has correctly identified the flaw in your writing and that you've selected the answer. Great! So I won't ...
jonk's user avatar
  • 78.3k

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