Questions tagged [circuit-theory]
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127 questions
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Equivalent impedance seen into drain
I can't understand or simplify the Zx in the picture
is equal to that of
- 37
2
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2
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104
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Complex Power Conservation or "Boucherot's Theorem" - a proof without Nodal Analysis
Brief Question
I'm trying to figure out a proof for the Complex Power Conservation Theorem, which does not use Nodal Analysis.
Theory I know
In my university this theorem has ben taught with the name &...
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2
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79
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How basic wireless electricity transmission circuit works?
In the circuit below because of the DC voltage source there will be no flux change on steady state of the circuit so how the LED still stays turned on if magnetic flux is not changing and no ...
- 99
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4
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129
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Can we solve all linear circuits using only KVL and constitutive relations?
Can We Solve for Node Voltages and Branch Currents in Any Linear Circuit Using Only KVL and Constitutive Relations?
In circuits with a single loop, it's trivial to solve using only Kirchhoff's Voltage ...
- 270
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Does KVL guarantee identical voltages/currents in similar circuits?
I have a question that is a bit abstract. Assuming I have two proper linear circuits, A and B, which have:
The same ideal components (for example, voltage source, inductor, capacitor, resistor)
The ...
- 270
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3
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134
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Power dissipation in an IC
Here is LM741 op amp circuit in Figure 1. The amplifier has two power supplies \$V_{cc}\$ and -\$V_{ee}\$. The up arrows are connected to the positive power supply \$V_{cc}\$ which is +15 V. Current ...
- 1,116
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2
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130
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Transient circuit analysis with additional source
The circuit in the image below is what I get when I open the switch of a larger circuit which I have already analysed. Therefore, I know the initial condition.
simulate this circuit – Schematic ...
- 147
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4
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143
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Are voltage ratings defined differently for capacitors and light bulbs?
The voltage rating of a capacitor is the maximum operating voltage, while the voltage rating of a light bulb is its normal operating voltage. Are there two different definitions of voltage ratings, or ...
- 270
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2
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How can I infer a circuit topology only from measuring/controlling its input and output?
Let's have a circuit only composed of resistors connected in a given topology. This topology (network) has a well defined boundary (input/output connectors) but otherwise we don't know how it is ...
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2
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162
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IV curve arithmetic - reference request
When playing around with electrical concepts in my head, I realized that the IV characteristic of any combination of elements, in series or in parallel, can be computed by simply adding the IV curves ...
- 243
1
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2
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266
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How to write the equation for the input side of a JFET?
I have been reading about the voltage gain of JFET, but I am unable to understand how to write the equation for the input side. Can somebody explain the method to write the equation for the input ...
- 147
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1
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175
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Resistive network with two voltage sources
Update: (I updated the description/Question for clarity)
I am currently stuck trying to solve a seemingly simple resistive network. The voltages U1 and U2, aswell as Rr are known. The unknown ...
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2
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195
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Why doesn't mesh analysis work here?
I am new to theory of circuits and I just learned about mesh analysis. When I was doing some reviewing, I stumbled across this question and wonder if you can use it here:
I plugged the equation into ...
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1
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1
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104
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Transient Charge Density in Conductor
Veritasium's (Derek Muller's) video How Electricity Actually Works makes the claim at
4:44 that:
The truth is, if you average over a few atoms, you find the charge density everywhere inside a ...
- 27.8k
1
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1
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59
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Computing input resistance of two common-base configurations
When computing the input resistance of this common base configuration, the collector current \$I_C\$ is approximated as equal to the emitter current \$I_E\$:
simulate this circuit – Schematic ...
- 748
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1
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119
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Combining cable resistance and law of resistances in parallel circuits
For a parallel circuit it is true that
\$1/R = 1/R_{1} + 1/R_{2}\$
Consider two equal cable switched parallel to each other. Their individual resistance is \$R = phi * l * A\$, where phi is constant.
...
- 103
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4
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3k
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Does a resistor between two pairs of series resistors affect the equivalent resistance?
For the below DC circuit, does the 1Ω resistor in the middle have an effect on the equivalent resistance?
If it does, how would you calculate the equivalent resistance? The rules for series and ...
- 191
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2
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277
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How to find a missing resistor?
This seems to be a really simple question. I'm not really sure where I went wrong in my solution. Please forgive me if this seems irritatingly simple, I've only just started learning about electric ...
1
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1
answer
291
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How to simplify this complex DC circuit?
I find it very hard to simplify this circuit. Currently practicing for my removal exam and this was one of the problems I failed on one of my previous exams.
Especially the middle part makes me so ...
6
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1
answer
1k
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What is the maximum current of an electronic load?
Here is the specification of an electronic load:
If the load is set in current mode, the current is limited to 25 A.
Nevertheless, if the current is set in resistor mode, I could think that it is ...
- 2,610
2
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2
answers
122
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Good way to obtain voltages along (non-uniform) \$RC\$ line
I have a long RC line, e.g.:
simulate this circuit – Schematic created using CircuitLab
Is there a good way to obtain the voltages on nodes V1, ..., Vn (possibly approximated) at a specific ...
- 1,332
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4
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764
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Synthesizing an impedance given by transfer function (poles/zeros) using a passive network
I would like to synthesize an arbitrary passive network based on a given transfer function (poles/zeros).
The origin is the output impedance of a voltage regulator for which I want to find an ...
- 1,332
0
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0
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189
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Transistor analysis with 2 voltage sources
I want to calculate the DC currents of this circuit, and based on the superpostion theorem, I thought of ignoring Vqdc9 first, in order to calulate I2, I21 and I22, as shown in figure 2. After that, I ...
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3
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542
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How do I use Norton's Theorem to find the current in this resistor? [closed]
I've been trying to solve this question but it seems impossible
0
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308
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Mesh Current Method and Analysis DC
This is my approach so far:
simulate this circuit – Schematic created using CircuitLab
I'm having problems with the third loop, only because of the fact that there are two batteries that are ...
2
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2
answers
3k
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Do higher voltages cause heating?
I'm trying to wrap my head around energy consumption in general.
For some background info, I'm an engineering student and am familiar with the usual electrical engineering formulae
Here is what caused ...
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2
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1
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204
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How do you prove that a certain circuit is impossible to construct with a certain amount of switches?
I wanted to make a subcircuit, which, if viewed as a black-box, is a two-terminal device, which can behave as
a closed circuit (0 Ω)
25 Ω
50 Ω
an open circuit (∞ Ω)
(sans non-idealities of course; i....
- 5,497
2
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3
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921
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Is it possible to constrain a circuit's voltage supply to a specific voltage range?
I have a circuit which requires exactly 12v to work properly, with a maximum tolerance of ±0.5V. The circuit is arbitrary and one can think of it as a theoretical question, but let's say that it ...
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1
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396
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Books on network theory [closed]
I really want to know which books should I read to learn the subject- Network theory in electrical engineering.
I know there are some popular books out there in the market, but I will really ...
6
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3
answers
624
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Is reactive power periodic in nature? What is the exact difference between active power, average power, and real power?
Consider an RC circuit which is supplied by a sine source
$$v(t)=V_m\cdot \sin(\omega t)$$
The current through the circuit will be
$$i(t)=I_m\cdot \sin(\omega t+\phi) \\
\phi=\arctan \left(\dfrac{1}{\...
0
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1
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243
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Why reactive components have less influence at low frequencies?
Some textbooks state that reactive components (may) have less influence at low frequencies, since inductance and capacitance are generally more significant at hifh freqs. "Pratical electronics ...
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2
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1
answer
185
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How to analytically find node voltages in a voltage doubler?
Given a voltage doubler circuit:
simulate this circuit – Schematic created using CircuitLab
You can figure out what should happen in stead state if \$R_L=\infty\$ and \$R_s=0\$. In that case, \$...
- 2,116
1
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1
answer
357
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Meaning of the determinant of an ABCD transmission matrix
In a thesis, [1] I found the following statement:
To determine [characteristic impedance and] dispersion relationships for
an arbitrary reciprocal network having the transmission matrix
$$ \begin{...
- 1,332
2
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2
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121
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Why losslessness requires voltage and current must be both zero?
In the textbook (pg. 260 Linear Circuit Analysis, by Artice Davis), losslessness is defined in such way:
Losslessness: If w(\$\infty\$) = 0 for any v(t) and i(t) waveforms supported by the
element ...
- 1,448
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0
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90
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NgSpice transient analysis on BJT Colpitts oscillator
Can you tell me how can I run a transient analysis on it? What I am curious about is the startup process.
I'd use a simple textbook example BJT circuit, the point is on the simulation setup/commands.
...
- 205
3
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1
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224
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Clarifying an article on switch debouncing - something about leakage current causing trouble
I recently read this article on switch debouncing: A Guide to Debouncing - Part 2, or, How to Debounce a Contact in Two Easy Pages, by Jack Ganssle.
The article is on choosing the correct resistor and ...
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0
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146
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Understanding MOSFET operating transitions
I'm trying to conceptually understand the output voltage and the operating condition transitions that the MOSFETs in the circuit below go through as the input voltage is swept from 0 to VDD.
It's not ...
- 705
0
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1
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188
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Diodes and resistors theory
I came across a problem which I cannot calculate by theory.
How does this circuit with diodes and resistors work?
In the above diahram, I can calculate the current simply by subtracting the voltage ...
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221
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Causes for negative port resistance of passive device (or obtaining |S11|>0 from measurements)
Suppose you have two reciprocal (passive) devices, A and B, both described with S-parameters \$S_a\$ and \$S_b\$. With a VNA, you measure \$S_a\$ and \$S_{\rm tot}\$ (S-parameters of AB, both devices ...
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1
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612
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How to deal with a negative resistor in Z parameters of a passive network?
This question is so basic but for some reason I am not seeing it: Assume an arbitrary passive 2-port network having only isotropic materials. This implies S21=S21 and Z12=Z21 (see https://www....
- 1,332
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0
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26
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Multipole Network Power Calculation
How do we calculate the DC power consumption of a multipole resistive network, if we know the currents of all the poles (pins) and all the voltages between the poles?
Let's say for example, that we ...
- 561
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1
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1k
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Transfer function and characteristic equation
I have the following network (page 805, example 14.5, Agarwal & Lang, Foundations of Analog and Digital Circuits):
The associated transfer function for \$i_z, v_z\$ is \$ H(s) = \frac{I_z (s)}{...
- 705
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221
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Complex impedances of capacitors/inductors in the phasor domain
I'm trying to verify the complex impedances of passive components in the phasor domain (not s-domain). Take for example the inductor, whose element law is \$ v = L \frac{di}{dt} \$. Assuming a complex ...
- 705
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2
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2k
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dependent current source polarity
In this question, I apply the current cycle law,
I find the current i1 to 25uA. I find the voltage on the dependent current source -2 volts. When I go through the formulas, there is no problem here.
...
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2
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237
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Transient solution of current in circuit with two coupled inductors, with resistances
Circuit in question is given below. I want to find why I can not get the
same current waveform as PSpice gives me.
Basically I want to calculate formula for i1(t) by hand and get something as close ...
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3
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1
answer
644
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Why is this two-inductor circuit first order?
I have the following circuit with two inductors. Apparently this is a first order circuit (judging from my solutions for \$ i_1, i_2\$; and circuit simulations) but it's not intuitively clear to me ...
- 705
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1
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233
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Confusion Between Dual Capacitor/Inductor Circuits
I'm trying to physically understand the responses of this pair of (dual) circuits: a step current source driving a capacitor and a step voltage source driving an inductor.
simulate this circuit &...
- 705
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4
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159
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Energy Transport in Circuits
I've been reading about how energy is actually transported in circuits (I first read about it here: http://amasci.com/miscon/ener1.html). The description in this article of why electrons don't move ...
- 705
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4
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287
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Relation between transmission line and circuit impedance
What is the relation between the impedance of lumped components and the characteristic impedance of transmission lines?
I have noticed that in some cases transmission lines are loaded with lumped ...
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2
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1
answer
93
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Maximum error of nominal resistor combinations
Suppose you have resistors which have nominal values of \$R_0\$ or \$2R_0\$ but can vary to be anywhere between \$(1 ± .03)R_0\$ or \$(2 ± .06)R_0\$, respectively, so each can have about 3% error.
...
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