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Chem Bio > ELECTRONICS > Flashcards

ELECTRONICS Flashcards

1
Q

What is a mesh?

A

A loop that does not contain other loops

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2
Q

What is a KCL in regards to nodes

A

Sum of all current leading to a node = 0 (conservation of charge( so if all currents facing the node - the sum = 0 if some facing and some moving away then can rearrange to that sum of those moving away equal those going towards

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3
Q

Practice breaking circuits down into parallel and in series resistors

A
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4
Q

Know unit conversion (Charge, Voltage, Current and Powah)

A

Charge is in coulombs - 1.6E-19
Voltage is volts = 1 J/C
Current is I in amps - its C/s
Power is Watts and P = IV (also I^2 /R or V^2/I
(and of course V = IR

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5
Q

What is resistivity?

A

resisitivity is an inherent property of a material (unit is ohm m) - Resistance as a whole depends on geometry of as well as resistivity
So R = p *(L/A)

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6
Q

What is conductance?

A

Inverse of Resistance (1/R) - its G

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7
Q

Know how to calculate max wattage a resistor can take- eg 1000 Watt hair dryer - 120 V outlet - what can the max resistance be

A

W = IV so 1000 = 120 * I
I = 8.33
120 = 8.33 * R
R = 14.4

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8
Q

Difference between Ideal voltage and current source

A

Idea lvoltage source-
Output voltage doesnt change -
0 internal resistance -
Current changes based on load

Ideal current source -
Load doesn’t effect output current
(voltage changes based on load)
and infinite internal resistance

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9
Q

Branch vs node

A

branch a portion of circuit with 2 terminals
Node - a junction of 2 or more branches

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10
Q

What is KVL kirchoffs voltage law

A

Sum of the voltages around a closed loop is 0
eg so if have 2 sources their sum = 0

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11
Q

Know KCL and KVL in a circuit

A

So in series I is the same and V is the sum of V’s
R is the sum of the R’s

In parallel I is the sum, V is the same and R is(1/R = 1/R +1 /R + 1/R)(so int his case - conductivity is summed G is sum of G’s)

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12
Q

So what is voltage divider and how can it beused

A

Basicaly a bunch of things in series - if we have a bunch of resistors in series its a voltage divider - If there are a bunch of resistors in a row the voltage we measure can vary based on how much of the resistors we are measuring across

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13
Q

Whats a current ddivider -

A

A bunch of resistors in parallel

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14
Q

Practical vs ideal voltage source

A

Has internal resistance or impedance
But basically if the internal resistance is «< Rl (resistance of load) can essentially say that the vl = vs (voltage across load equals that of V source

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15
Q

Practical current source

A

internal imedance infinity - So the OUTPUT current depends on R - look at derivation for that - KEY HERE IN DIAGRAM THEN - our internal resistance is PARALLEL to our load resistance
So we see the opposite relationship where rs»> Rl then Is = Il(go through derivation)

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16
Q

How to measure voltage with a DMM (talk about loading error)

A

You want to do it in parallel with a resistor (in parallel voltage remains the same)
However to minimize loading error you want the DMM to have Very high resistance such that the R equivalent for this parallel part essentially just equals the resistance of the resistor in circuit
(DO OUT THE math - For our parallel section with the DMM the Req is 1/Req = 1/Rc + 1/Rdmm
Which turns into :Rc*Rdmm / (rc + RDmm)
SO if Rdmm&raquo_space;> Rc then it just turns into Rc which is what we want - reflects the circuit

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17
Q

When measuring current with DMM what do we want

A

We want it in series with minimal resistance (so again thinking of resistance - in series add them up - soto make the equivalent resistance = the resistance in circuit want Rc»»> RDmm

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18
Q

Loading error equations fo measuring DC voltage

A

Essnetiall % error for V
(so V load - V battery / V battery)*100
OR for REsistor ITS different
-Rt / (Rt +Rm)
Note m is the load or meter and T is the soruce
NOTE always negative error because ITS always less than
NOTE -larger DMM resistance makes or error smaller

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19
Q

Measuring DC current error

A

% error for current again
and for Resistance
Er = - Rm/(Rn + RM) x 100
RM being fo the load I belive
LOADING ERROR DECREASES WITH SMALLER DMM RESISTANCE which we showed

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20
Q

Steps for KVL analysis

A

Draw current direction
Define clock wise or countercloskwise to sum voltages (use the same convention in every loop) - APPLY THE KVL (V in series should add up to 0 (or to the battery amount)
Or can apply kirchoff current law (at a node the sum of current s= 0

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21
Q

What is a Thevenin netwooork

A

Basically any network of sources and resistors can be seen as a voltage source and resistor in series (Vt is voltage source) and RT is resistance of netowrk

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22
Q

Norton Equivalent Circuit

A

Same idea as thevening but a CURRENT source and a parallel resistor - r = Rn

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23
Q

What is the relationship between Rt and Rn (thevenin and norton)

A

Rt = Rn

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24
Q

How to calculate Thevenin Resistance Rt

A

Take away voltage source replace with wire (note we’re calculating resistance Load sees) - so then we turn the remaining resistors into one equivalent resistor in regard to the load (in Voout or a b

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25
Q

Thevenin get the open circuit voltage

A

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

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26
Q

Calculate the Short circuit Current

A

See slide about how to do - go over study guide

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27
Q

How to generate Alternating Current

A

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

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28
Q

Why do we use AC over DC

A

motor and generator design simpler and more efficient

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29
Q

Whats the fourier theorm

A

Can construct any other waveform by adding sinusoid of different frequencies

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30
Q

What are the parameters of a sin wave

A

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?)

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31
Q

How does phase effect sine waves

A

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

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32
Q

IV relationships in AC circuits how do they change (implications on power)

A

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)

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33
Q

CAPACITOR EQUATIONS

A

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

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34
Q

How does a capacitor work and what do they do

A

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

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35
Q

How do capacitors add

A

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

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36
Q

Does current flow through a capacitor?

A

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

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37
Q

How does our capacitor react in regard to a sin wave

A

So if we’re thinking current - its share in Q charge over time - which equals CV (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

38
Q

How does current relate to Ip with sin wave

A

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

39
Q

Given Ip = C*Vp what does that mean for reactance

A

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)

40
Q

How to get impedance of RC circuit (or derive it)

A

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)

41
Q

How do you make a low pass filter

A

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

42
Q

Whats BODE diagram

A

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

43
Q

Complex # form

A

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

44
Q

complex numbers in cmplex plane

A

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)

45
Q

What is the polar conversion of z* = a- jb and z = a + jb

A

abs(Z)e^(jtheta) or abs(Z)e^(-jtheta)

46
Q

When use cartesian vs polar

A

add subtract for cartesian - multilpy divide for polar

47
Q

Voltage in ac circuuit

A

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

48
Q

Voltage across capacitor vs voltage across resistor in RC circuit in terms of vs

A

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

49
Q

How does frequency effect ouput?

A

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

50
Q

How do you define Vo and Vi when determining gain for a capacitor then a resisto rin series

A

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

51
Q

Gain function equation! for high pass filter?

A

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

52
Q

tALK ABOUT HALF POWER POINT - WHAT THINGS ARE TRUE DURING IT

A

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

53
Q

what are the two types of BODE plots

A

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

54
Q

Low pass filter for gain vs high pass

A

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

55
Q

2nd order vs 1st oder filter comparisons

A

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

56
Q

Describe basics of inductors

A

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.

57
Q

How do inductors work in basic circuit addition

A

in series add, in parallel combine like resistances

58
Q

What does inductor do in DC circuit

A

Is a wire

59
Q

indcutvei resistance

A

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

60
Q

General rule for determining what kidn of filter something is

A

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

61
Q

What is an RLC bandpass filter

A

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

62
Q

What is the max gain on an RLC band pass

A

when w = 1/(ROOT(LC))

63
Q

Q factor of RLC

A

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

64
Q

How do you make a band stop filter?

A

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

65
Q

What is a semicondcutor

A

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!

66
Q

What is the typical semiconductor interaction

A

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)

67
Q

What is a forward biased vs reversed biased diode

A

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

68
Q

Whats BJT -

A

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

69
Q

What is current gain

A

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

70
Q

Genereal relationships between base cu[rrent and coelctor current

A

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

71
Q

Key Points about MOSFETS

A
  • 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
72
Q

OPAMP - ideal input impedance is?

A

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

73
Q

What is the amplifier output resistance

A

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

74
Q

What are the characteristic sof op amp

A

hugh voltage gain, high inut impedance and low output impedance

75
Q

Whats the problem with just traditional op amps -

A

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

76
Q

What are some basic neg feedback loop equations

A

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+AoB)
with Af being the actual gain and Ao being initial gain
Af = 1/B (typically assuming that AoB»»1

77
Q

Why are negative ffedback opamps good

A

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

78
Q

Types of OPAMPS

A

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&raquo_space;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

79
Q

Explain current follower

A

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&raquo_space;iB) so ii = if
vo = -if*Rf 9dependant on feedback loop)
Ri = Rf/A (input resistance )

80
Q

Explain inverting amplifer omp amp

A

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

81
Q

Explain adder

A

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

82
Q

OP AMP INTEGRATOR

A

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

83
Q

OP AMP DIFFERENTIATIOR

A

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

84
Q

NON INVEFRTING AMPLIFIER -

A

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

85
Q

WHY INERTI OR NON INVERTINY

A

NON INVERTING HAVE HIGH INPUT IMPEDANCE inverting typically low input impedance

86
Q

Differential siubtractor amp

A

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

87
Q

INSTRUMENT AMPLIFIER

A

start with 2 op amps go into one

88
Q

Golden rules of neg feedback

A

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

89
Q

How does frequency effect opamp gaine

A

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

90
Q

What is SLEW

A

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

91
Q

Positive vs negative feedback loop

A

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

92
Q

positive feedback use

A

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

Chem Bio (17 decks)

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