Questions tagged [formula-derivation]
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10
questions
1
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1answer
9k views
I/O Resistance of common source MOSFET with source degeneration
Common Source MOSFET with source degenerations looks like this
I am a bit confused about different input and output resistance statements (provided by different sources).
Some of them say that ...
0
votes
2answers
404 views
MOSFET Biasing Problems
I am interested in finding Vgs for E-MOSFET for desired Id or/and Vds. Referring to those equations of drain current in saturation region, value of conduction parameter "K" would be nice to have but ...
0
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2answers
2k views
Common drain JFET output resistance “problem”
The output resistance of small signal model for common drain JFET amplifier equals $$ \frac{1}{g_\text{m}} || R_{\text{ds(on)}} \parallel R_\text{S} $$ and since $$ R_{\text{ds(on)}} =\frac{1}{g_\text{...
1
vote
3answers
4k views
Common Source JFET small signal equivalent circuit
This circuit is equivalent to small-signal common source JFET amplifier:
If you look at the input and output impedance you can see that Zin = R1 || R2 and Zout = rd || Rd || Rl. It can be seen from ...
7
votes
2answers
24k views
Deriving the formula from 'scratch' for charging a capacitor
So the formula for charging a capacitor is:
$$v_c(t) = V_s(1 - exp^{(-t/\tau)})$$
Where \$V_s\$ is the charge voltage and \$v_c(t)\$ the voltage over the capacitor.
If I want to derive this formula ...
13
votes
3answers
5k views
Why is inductance (L) proportional with turns-square (N²)?
We start from the Maxwell's Equation
$$
\mathbf{\nabla} \times \mathbf{B} = \mu \mathbf{J} + \overbrace{\mu \epsilon \dfrac{\partial \mathbf{E}}{\partial t}}^0.
$$
We take surface integration of ...
1
vote
1answer
231 views
math behind complex numbers C||RLC
I have a mathematical problem with the following formula.
The goal is to transform this equation to have a seperated real and imaginary part.
I have already done this with several other equasions, but ...
2
votes
4answers
9k views
How to Derive Capacitive- and Inductive Reactance Formula
I've been searching around the internet to find out how to derive the reactance formula for capacitors and inductors. But I couldn't really find anything, so I thought why not make a post about it.
...
0
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3answers
1k views
How to differ output & input resistance of small-signal model BJT?
I understand how input and output resistance of small-signal model for bipolar transistor is defined and how draw one.
What I don't understand quite yet is how actually input and output resistance of ...
0
votes
1answer
4k views
Bypass source capacitor JFET
I know there were some changes applied to voltage amplification formula of BJT when "Ce" (emitter bypass capacitor) was connected to the circuit. How is it with JFET (MOSFET too) and its bypass ...
