ELECTRONICS Flashcards

Question

Thevenin get the open circuit voltage

Answer 1

Remove the load Equal tot he voltage across the parallel resistor -

Answer 2

See slide about how to do - go over study guide

Answer 3

Current through a wire creates a magnetic field - you then have 2+ coils of wire placed so the changing magnetic field in one induces a voltage in the other - So basically we have an AC source we apply to one coil (energize it) - ti will create an AC voltage in the other coil

Answer 4

motor and generator design simpler and more efficient

Answer 5

Can construct any other waveform by adding sinusoid of different frequencies

Answer 6

Frequency - 1/t # of cycles past a point in unit time0 w = 2 pi * f (rad/s) (angular frequency) (change in angle over time) v = Vpsin wt (note Vp is peak V) I = Ipsinwt (I is peak I?)

Answer 7

Have 2 AC batteries - If both in phase - additive if one out of phase - subtract em

Answer 8

Not much really - V just becomes Vpsin(wt) so if one resistor in a loop voltage across it is Vpsin(wt) If want current across it its just (Vpsin(wt))/R So for Power - P average = Irms * Vrms Also can do Joule Heat in resistor (called effective DC signal)

Answer 9

C = Q/V (q quantity of charge in coulombs) and C is capacitance in Farads Q = CV

Answer 10

Important because means a VOLTAGE change can lead to a time varying charge (charge per time) (or current) So we get a current change following our voltage change

Answer 11

inverse of resistors - so in parallel add them up - in series its 1/C = 1/C + 1/C

Answer 12

NO in DC nothing - in AC its charging and discharign MIMIC the AC current

Answer 13

So if we're thinking current - its share in Q charge over time - which equals C*V (which is dV/dT because its not I its really dI/dT) V we know varies with sin wave so we can make that C* dVpsin(wt) /dt which if simplified becomes wCVpcos(wt) which is the equivalent to wCVpsin(wt + pi/2) which is where we get the idea that OUR current is 90 degrees off from our voltage (current leads coltage0

Answer 14

i = Ipsin(wt + pi/2) as such Ip = C*Vp

Answer 15

that means C = Ip/Vp or 1/C = Vp/Ip which is we sub in Ip for wCVp - we get 1/wC Which means our reactance is in fact frequency dependant also w = 2 pi so 1/(2pifc)

Answer 16

So this is a vector diagram where resistance is along the x and reactance is imaginary - down the y axis (negative ) - SO it's just a right triangle so Pythagorean - so its just ROOT( R^2 +C^2) which we have the specific equations for each additionally if we want the angle for this vector its just arc tan (opposite over adjacent which is just C/R)

Answer 17

have a capacitor in series with a resisto r(parallel to where measuring) - the idea being the signal at capictor cannot be low frequency or else circuit doesn't work Its a voltage divider so the voltage at the resistance is proportional (R/(R+C) or R/Z Can also do the same thing but measure across the capacitor

Answer 18

frequency repsonse vs magnitude (frequency against 20log(Vpo/VPin_

Answer 19

z = a +bi a - is real part b is imaginary part (b is real # times root (-1) in electronics use z = a +jb z = a-jb is the conjugate

Answer 20

a = abs(z)cos theta b = abs (z) sin theta abs z = root of a^2 + B^2) so a is our x axis and b is our y axis z is the sum angle theta again is arctan (B/A)

Answer 21

abs(Z)*e^(j*theta) or abs(Z)*e^(-j*theta)

Answer 22

add subtract for cartesian - multilpy divide for polar

Answer 23

V = I*Z (see deri - dont need to know)

Answer 24

vc is vs * (1/(jwrC+1)) vr is vs *((jwrc)/(jwrc+1))

Answer 25

changes current and voltage DUE to change in impedances - this is key for ATTENTUATION - is the term for this (jw/jw) - for passive circuit lesss than 1 - for active circuit - any value posibble

Answer 26

Vi is Z and Vo is R (so its R/z which is jwrc / (1 + jwrc)

Answer 27

wrc / (root(1 + (wrc)^2) AND THETA = (PI)/2 - inversetan(wrc) (phase degree)

Answer 28

so w = 1/RC (makes our wrc / (root(1 + (wrc)^2) equation 1/root(2) That means gain is 1/(ROOT(2) or 0.707 essentially po/pi = 1/2 it's -3db phase angle is 45 degrees

Answer 29

magnitude plot - frequency in response to db or gain and the PHASE plot - phase shift in regard to frequency

Answer 30

low pass is R then C - high pass is C then R - so they essentially switch Vo is Zx while V in is Z(C +R?) - which makes essentially the same equation but (1 / (ROOT(1+(wrc)^2)) BUT its the same in that when w = 1/RC we get our half power point

Answer 31

1st order 3db is half power point - loses 20 db per decade (hence log 20) 2nd order is double 6 is our half power point and lose 40 per decade

Answer 32

inductance is L v = L *di/dt measured in henrys Enegry stored is W = 1/2 (LI^2) An inductor is a passive electronic component which is capable of storing electrical energy in the form of magnetic energy. Basically, it uses a conductor that is wound into a coil, and when electricity flows into the coil from the left to the right, this will generate a magnetic field in the clockwise direction.

Answer 33

in series add, in parallel combine like resistances

Answer 34

jwl (zo overall Z(impedance) is R + jwl

Answer 35

I guess in parallel - the first determines filter type the second is used to build resistance (so a capacitor on the front means high end pass ) but if its second we want the signal that builds resistance so resitor then capacitor is low end pass

Answer 36

lets through a certain band - C lets in high pass F only lets in low pass so get something in the middle (so L then C then R parallel to load

Answer 37

when w = 1/(ROOT(LC))

Answer 38

quality factor - indicates the selectivity of the circuit (basically like resolution - how narrow this peak is - its (w*L)/R and typically adjust through R

Answer 39

essenitally like a band pass filter BUT you read across the L and C as opposed to the R (same idea ) - R means filtering nothing) - and we generate resistance across the two extremes

Answer 40

crystalline -conductivity between a conductor or insulator - all of outer electorns are PERFECT covalent bonds but we dope them to create holes and free electorns N doped - means there is group V element - so free electrons P doped - means group 3 elements and there is a hole!

Answer 41

we got a p junction and an N junction and essentially there is attraction at the junction - combining of electrons and holes - depletes oles in p region and electorns in n region near junction (builds up an electric field)

Answer 42

forward bias can allwo current through - essentially the current goes into the p region (or + charge does) which pushes the holes of the p region to the junction which attracts the negative charge there allowing the positive charge to continue IN a reverse biased - the negative charge goes to the p region and the holes are atttarcted to that (and vice versa) and you get DEPLETION - no interaction

Answer 43

bipolar hunction transistor - basically have a channel - so basically either PNP or NON - emitter base and collector - can tell direction because it always goes P to N

Answer 44

Beta = Ic/Ib Collector current is controlled by BASE current - so as w change base current the collector current is modified

Answer 45

a smaller base current effects the collector current more so greater gain

Answer 46

* FETs are widely used in both analogue and digital circuits * They have high input resistance * There are two basic forms of FET: MOSFETs and JFETs * MOSFETs may be divided into DE and Enhancement types * In each case the gate voltage controls the current from the drain to the source * The characteristics of the various forms of FET are similar except that they require different bias voltages * FETs can be used to produce various forms of amplifier and a range of other circuit applications

Answer 47

infinity! - because we can see the thevenin form - where its read across R in - BUT the amount of voltage that goes to r in is split across r in and r input (Rs) so if Rinput is massive- these spit essentially becomes all for r input and not for input resistance

Answer 48

Shoudl be 0 for kidn of the opposite reason - what the amplified v out to be 100% of V in and again its split and want it to all be across our Rl

Answer 49

hugh voltage gain, high inut impedance and low output impedance

Answer 50

no flexibiltiy and cvery low voltage range - maxes out very ease v+ to v- is small (also not stable and linear (NEED FEEDBACK

Answer 51

Ao open look voltage gain = vo/v' (v' being adjusted input) v' = vi = Bvo (B being the fraction of vo fed back Af = Ao/(1+Ao*B) with Af being the actual gain and Ao being initial gain Af = 1/B (typically assuming that Ao*B>>>>1

Answer 52

CIRCUIT PROPERTIES ONLY DEPEND ON EXXTERNAL FEEDBACK NETWROK SO SUPER CONTROLLABLE( also helps with non linearity improves response etc)

Answer 53

if the negfeedback loop is wire - THIS IS A BUFFER - just used to minimize loading error due to high input impedance and low output impedance (voltage follower) Current follower = Have input as current source and a resistor on feedback loop VIRUTAL common potential (V+ = V-) Essentially NONE of the current goes to opamp but goes to resistor (iF >>iB) so ii = if vo = -if*Rf 9dependant on feedback loop) Ri = Rf/A (input resistance ) INVERTIN AMP -has a resistor before the invert input Close loop gain - Af = -Rf/Rs = (vo/vs) here is = -if which is essentially the same as before so vo = -RF/RS * vs Voltage ADDER -its a combo adder and multiplier - the adders are in parallel and each factor is multiplied by what we stated before rf/rs

Answer 54

Current follower = Have input as current source and a resistor on feedback loop VIRUTAL common potential (V+ = V-) Essentially NONE of the current goes to opamp but goes to resistor (iF >>iB) so ii = if vo = -if*Rf 9dependant on feedback loop) Ri = Rf/A (input resistance )

Answer 55

INVERTIN AMP -has a resistor before the invert input Close loop gain - Af = -Rf/Rs = (vo/vs) here is = -if which is essentially the same as before so vo = -RF/RS * vs

Answer 56

Voltage ADDER -its a combo adder and multiplier - the adders are in parallel and each factor is multiplied by what we stated before rf/rs

Answer 57

also has a capacitor in parallel with the feedback loop reset switchch (also has a hold switch) dvo/dt = vC*R Vo = 1/RC * integrated (vidt) takes a square wave and makes it min max wave (I forget the name)- basically since integrates give the slope - so good as waveform generator

Answer 58

Here the capacitor is before the op amp Vo = -RC Dvi/dt Basically only spikes when there is a change in signal

Answer 59

goes in both + and negative both have a reistor before NOTE source at Positie Gain = 1 + Rf/Rs again dependant on the top one

Answer 60

NON INVERTING HAVE HIGH INPUT IMPEDANCE inverting typically low input impedance

Answer 61

OK so 2 inputs each has a resistor - Positive goes to ground and negative goes to vo out if BOTH change together its common mode - if change independently - normal mode a GOOD ONE HAS A HIGH CMMR - common mode reject ratio v out - Rf/Rs (vs - v1) CMMR = Ad/Acm So better CMMRR means better at rejecting common mode signal - useful for removing noise Ad is ratio of vo compared to (v2-1) and Acm is ratio of Vo to V2

Answer 62

start with 2 op amps go into one

Answer 63

voltage at input is the same and no current to op amp (except when sat)

Answer 64

Af *fo = ft - as it goes up - gain goes down until it reaches unit - NO GAIN

Answer 65

s = dv/dt - basically the idea that there's lag - vo out doesn't match vi immediately can deal with slew issues by decreasing frequency, lowering A (gain) or lowering in put signal

Answer 66

changes where it goes - if loop on positive its positive if its on invertor its negative which makes sense

Answer 67

to staurate - get max (eg turns sin wave into max) or also to dea with noise -very much like a binary on off switch