Electronics Engineering

The difference between academic and casual communication. Casual communication is more of socializing with family and friends and co-workers and academic is speaking in a more professional manner. Adhering more to the words and the proper language use. You would not normally speak in a professional manner on a daily basis unless you are in a professional surrounding 24/7.

PNP Positive Negative Positive, is a type of Transistor. I don"t know of military applications.

Anode is positive, cathode is negative

A: first you must define the frequency of transmission. wave lenght is time from that you can calculate them total time

A: Any amplifier will reach a frequency cut off point because of hindered circuit capability however the roll of bust be controlled especially when reaching oDB point must be at a -3 db roll off to prevent hi frequency oscillation

An inductor resists a change in current. The equation is ...

di/dt = V/L

... where di/dt is the rate of change of current in amperes per second, V is the EMF is volts, and L is the inductance in henrys.

Looking at this, you can see that the slope of the current is proportional to the voltage and inversely proportional to the inductance.

One characteristic of inductors is that when you have a current established, and then break the circuit, the inductor will respond by trying to maintain the current. If this is not possible, such as when the circuit is open, the inductor will generate a large reverse EMF - in the theoretical case, an infinite EMF - in the practical case, several thousand volts, depending on the inductor. This is why proper design of inductors in DC circuits, such as relays and solenoids, must include reverse EMF suppression, such as a diode or resistor across the inductor.

A: Absolutely a power transfer will have an internal loss of IR . for a power transformer the loss can be as much of 20% or more if other magnetics are involved like iron screw holding the lamination together. Usually brass is used to reduce that loss.

A: As current begins to flow the action on a resistance will be a voltage drop which is inversely proportional to the current. Making it a voltage amplifier as opposed to a tube where it is a current amplifier

diode:= di+ iode

di means two,and iode means terminal,,,, diode is two terminal device i.e anode and cathode

fets are used due to their high speeds

its a type of transformer oil which provides insulation ...

They are used as adjustable bandpass filters in superheterodyne (Google it) recievers. They determine how well you can select the radio station you require, while rejecting those close to it. They work in a fixed frequency range where their characteristics can be optimised.Very many modern radio recievers use some form of the superheterodyne principle though the function of the IF Transformer (ie bandpass filter) can be realised digitally, as in mobile phones for example. For AM radio a bandwidth of 9 KHz at 450KHz is typical.

The names of most ICs are just arbitrarily assigned numbers.

3 dB is a change in power by a factor of 2. If it is plus, i.e. +3dB, power is doubled. If it is minus, i.e. -3dB, power is halved.

6 dB, then is a factor of four, or quarter; 6 dB is a factor of eight, or eighth, etc.

The actual equation is 3 log2 (POWER OUT / POWER IN).

This is a simple derivation problem. Take the derivative of the AC voltage waveform (I'll assume sin (t)), and set the derivative equal to the maximum value it can attain (which is 1):

cos (t) = 1, t = 0 degrees, thus for an AC waveform of y = sin(t), the fastest increase in voltage occurs at 0, 360, etc. degrees. The fastest decrease in voltage will occur at 180, 180 + 360, etc. degrees.

Taking a step, feeling yourself imbalanced, and compensating by shifting your weight on the fly in order to maintain balance. You could simplify it further by saying that even just standing still requires a negative feedback loop in order to stay standing.

Thus if we go back to the

circuit model for the common emitter transistor, and

re-draw it as a small signal model it would look

something like Figure 1. Here we have replaced the

diode with a linear element (a resistor, called

rπ)

and we have changed the notation for the currents from

IB

and

IC

to

ib

and

ic

respectively, to remind us that we are now talking about small signal

ac quantities, not large signal ones. The bias currents

IB

and

IC

are still flowing through the device (and we will leave it to ELEC 342

to discuss how these are generated and set up) but they do not appear

in the small signal model. This model is only used to figure out how

the transistor behaves for the ac signal going through it, not have

it responds to large DC values.

Figure 1: Small signal linear model for the common emitter transistor

Figure 1 (3.16.png)

Now

rπ

the equivalent small signal resistance of the base-emitter diode

is given simply by the inverse of the conductance of the

equivalent diode. Remember, we found

rπ===1qkTIB1qkTICββ40IC

(1)

where we have used the fact that

IC=βIB

and

qkT=40V-1.

As we said earlier, typical values for βin a standard bipolar transistor will be around

100. Thus, for a typical collector bias current of

IC=1mA,

rπ

will be about 2.5 kΩ.

There is one more item we should consider in putting together our

model for the bipolar transistor. We did not get things completely

right when we drew the common emitter characteristic curves for the

transistor. There is a somewhat subtle effect going on when

VCE

is increased. Remember, we said that the current coming out of the

collector is not effected by how big the drop was in the reverse

biased base-collector junction. The collector current just depends

on how many electrons are injected into the base by the emitter,

and how many of them make it across the base to the base-collector

junction. As the base-collector reverse bias is increased (by

increasing

VCE

the depletion width of the base-collector junction increases as

well. This has the effect of making the base region somewhat

shorter. This means that a few more electrons are able to make it

across the base region without recombining and as a result

α and hence

β increase somewhat. This then

means that

IC

goes up slightly with increasing

VCE.

The effect is called base width modulation.

Let us now include that effect in the common emitter

characteristic curves. As you can see in Figure 3,

there is now a slope to the

IC(VCE)

curve, with

IC

increasing somewhat as

VCE

increases. The effect has been somewhat exaggerated in Figure 2, and I will now make the slope even bigger so

that we may define a new quantity, called the Early

Voltage.

Figure 2: Common emitter response with base-width modulation

effectFigure 2 (3.17b.png)

Figure 3: Finding the Early VoltageFigure 3 (3.18b.png)

Back in the very beginning of the transistor era, an engineer

at Bell Labs, Jim Early, predicted that there would be a slope to the

IC

curves, and that they would all project back to the same

intersection point on the horizontal axis. Having made that

prediction, Jim went down into the lab, made the measurement, and

confirmed his prediction, thus showing that the theory of

transistor behavior was being properly understood. The point of

intersection of the

VCE

axis is known as the Early Voltage. Since

the symbol

VE,

for the emitter voltage was already taken, they had to label the

Early Voltage

VA

instead. (Even though the intersection point in on the negative

half of the

VCE

axis,

VA

is universally quoted as a positive number.)

How can we model the sloping I-V curve? We can do almost the

same thing as we did with the solar cell. The horizontal part of

the curve is still a current source, and the sloped part is

simply a resistor in parallel with it. Here is a graphical

explanation in Figure 4.

Figure 4: Combining a current course and a resistor in parallelFigure 4 (3.19.png)

Usually, the slope is much less than we have shown here, and so

for any given value of

IC,

we can just take the slope of the line as

ICVA,

and hence the resistance, which is usually called

ro

is just

VAIc.

Thus, we add

ro

to the small signal model for the bipolar transistor. This is

shown in Figure 5. In a good quality modern

transistor, the Early Voltage,

VA

will be on the order of 150-250 Volts. So if we let

VA=200,

and we imagine that we have our transistor biased at 1 mA, then

ro==200V1mA200kΩ

(2)

which is usually much larger than most of the other resistors you

will encounter in a typical circuit. In most instances,

ro

can be ignored with no problem. If you get into high impedance

circuits however, as you might find in a instrumentation

amplifier, then

vbe

has to be taken into account.

Figure 5: Including ro in the small signal linear modelFigure 5 (3.20.png)

Sometimes it is advantageous to use a mutual transconductance

model instead of a current gain model for the transistor. If we

call the input small signal voltage

vbe,

then obviously

ib==vberπvbeβ40IC

(3)

But

ic=βib=βvbeβ40IC=40ICvbe≡gmvbe

(4)

Where

gm

is called the mutual transconductance of the transistor.

Notice that β

has completely cancelled out in the expression for

gm

and that

gm

depends only upon the bias current,

IC,

flowing through the collector and not on any of the physical

properties of the transistor itself!

Figure 6: Transconductance small signal linear modelFigure 6 (3.21.png)

Finally, there is one last physical consideration we should make

concerning the operation of the bipolar transistor. The

base-collector junction is reverse biased. We know that if we

apply too much reverse bias to a pn junction, it can breakdown

through avalanche multiplication. Breakdown in a transistor is

somewhat "softer" than for a simple diode, because once a small

amount of avalanche multiplication starts, extra holes are

generated within the base-collector junction. These holes fall up,

into the base, where they act as additional base current, which,

in turn, causes

IC

to increase. This is shown in Figure 7.

Figure 7: Ionization at the base-collector junction causes additional

base currentFigure 7 (3.22.png)

A set of characteristic curves for a transistor going into

breakdown is also shown in Figure 8.

Figure 8: Bipolar Transistor going into breakdownFigure 8 (3.23b.png)

Well, we have learned quite a bit about bipolar transistors in a

very short space. Go back over this chapter and see if you can

pick out the two or three most important ideas of equations which

would make up a set of "facts" that you could stick away in you

head someplace. Do this so you will always have them to refer to

when the subject of bipolars comes up (In say, a job interview or

something!).

The roll-off factor of a digital filter defines how much more bandwidth the filter occupies than that of an ideal "brick-wall" filter, whose bandwidth is the theoretical minimum Nyquist bandwidth.

The Nyquist bandwidth is simply the symbol rate expressed in Hz:

Nyquist Bandwidth (Hz) = Symbol Rate (Sym/s)

However, a real-world filter will require more bandwidth, and the excess over the Nyquist bandwidth is expressed by the roll-off factor. Suppose a filter has a Nyquist bandwidth of 100 MHz but actually occupies 120 MHz; in this case its roll-off factor is 0.2, i.e. the excess bandwidth is 0.2 times the Nyquist bandwidth and the total filter pass-bandwidth is 1.2 times the Nyquist bandwidth.

You cannot increase amperage without changing voltage or resistance.

Ohm's law states that voltage is current times resistance. You cannot change one alone.

Not even changing frequency in a capacitive or inductive circuit will do this, because changing frequency represents a change in reactance, which is effectively a change in resistance.

the sensistor functions as a temperature sensitive resistor with a positive coefficient of temperature.used for temperature compensation in various circuits

explain process, pcb and process state diagram.

1000 ohms

It depends on the size of the cord and the volts it carries-

But to find how much VOLTAGE a wire consumes...

It could be found by V = I X R

Usually the resistance of electrical wires is not TOO important- its important when you try to force large amounts of current through a long piece of wire. So lets say a wire is very long and was connected to a battery that had 15 volts and the resistance of the thin wire is 0.2, V=15 x 0.2 = 3 volts. Three volts is not a big deal if you have a high voltage power supply, but if you are using say a 12 volt car battery the length of the wire would take one quarter of the available voltage-which is why a automotive batteries cable is thick -to reduce its resistance below 0.2Ohms.

This is still sort of an in-direct answer- but it might help.