Solid State Midterms

Semiconductor

a material that is neither good at conducting nor insulating, but can be doped to do either

diode

2 way semiconductor which allows current flow in 1 direction and restricts it in the other

barrier voltage

a certain voltage dropped in order to achieve current flow

leakage current

any unwanted current flow outside of the desired circuit path

ripple

the variation in output voltage due to capacitor discharge

Q-point

the stead-state DC operating point of an electronic device

rectification

the process of turning an AC wave into a DC wave

voltage regulator

device that maintains constant voltage, even when input voltage or load changes

gain

a measure of a transistor’s ability to amplify an input signal

cutoff

a state of negligible conduciton

saturation

a region of operation of a transistor where it acts as a switch

amplifier

electronic device that can increase the magnitude of a signal

distortion

alteration of the original shape of a signal

bandwidth

a measure of width of a frequency range

frequency response

how well an amplifier performs over a range of frequencies

decibel

the unit for logarithmic gain

cascading

connecting the output of a stage to the input of the next

bias

the application of a DC potential to a transistor to ensure proper operation

Approximately how much of an AC cycle does a half-wave rectifier conduct? What about a full-wave rectifier?

half-wave uses half the wave, full-wave uses the whole wave both the negative and positive

What device is used as a filter in a rectifier circuit?

a capacitor

In what region of the diode characteristic curve does a zener diode operate?

breakdown region

What purpose does a voltage regulator serve in a circuit? Which device serves as a voltage regulator?

to limit or regulate a voltage to a stable value, zener diode

How do half-wave and full-wave rectifiers differ?

full-wave is more efficient since it uses the both halves of wave unlike the half-wave

Why is a resistor used in series with a zener diode?

to prevent too much current being drawn

How do you identify the cathode on a diode?

on the side with the striped band, triangle points towards it on the circuit symbol

Understand the basic construction of a transistor.

a base, collector, emitter, with P-type and N-type semiconductor material

What makes current flow in a transistor?

forward biasing the BE and reverse biasing the BC

Know the equation for calculating current gain in a transistor.

Ic/Bc

Understand what is indicated by the Q-point of a transistor. Where is it located on a dc load line?

the no-signal operating condition of the transistor

What materials are most commonly used to produce semiconductors?

silicon and germanium

What defines a material as P-type or N-type? What is each material used for in a semiconductor?

N-type has a negatively charged electrons, P-type has an excessive amount of positively charged holes, they create PN junctions

Be able to calculate the output voltage for a diode given the input voltage.

subtract the barrier voltage

What can be determined by testing a transistor with an ohmmeter?

the bias of the transistor

What is actually controlled by a transistor?

a larger current

Be able to calculate collector current given gain and base current.

current gain times the base current

List the three types of transistor amplifier configurations.

common emitter, common collector, common base

Where is the input signal applied in a common-emitter amplifier circuit? Where is the output signal taken?

the input is at the base and the output is at the collector

Vrms to Vp

Vp x .707

Vpp to Vp

Vp - Vl

Logarithmic voltage gain

20log10(Av)

Why does amplifier gain decrease at higher frequencies?

unavoidable parasitic capacitances and inductances within the circuit

Know how to calculate overall circuit gain for a two-stage RC-coupled amplifier.

product of the gains of each stage or (Vo2/Vi1)

Is the AC output voltage in a common-emitter circuit in or out of phase with the base voltage?

out of phase (180 degrees)

How much of the current from a transistor emitter terminal flows to the collector terminal? The base terminal?

98-99%

What happens when you connect a load across the second-stage output?

creates a voltage divider

How does the voltage at the base of an NPN transistor behave when operating in the active region?

the base emitter junction is forward biased

Know what occurs at the cutoff and saturation points of a transistor. Where are those points found on a dc load line?

at cutoff, transistor current is zero and CE voltage is max
at saturation, collector current is max and CE voltage is min
they’re the ends of a dc load line

What are the advantages of a common emitter transistor amplifier circuit?

it exhibits both voltage and current gain meaning more potential power gain

What is the purpose of the voltage dividers in RC-coupled amplifiers?

to establish a stable voltage

Why are multi-stage amplifiers advantageous over single-stage amplifiers?

allows higher gain

Where is the output from an RC-coupled amplifier developed?

across the parallel combo of Rc and and Rl

What is the difference in how AC and DC parameters are represented on a transistor specification sheet?

DC is usually found under ON CHARACTERISTICS and AC is under SMALL-SIGNAL CHARACTERISTICS

List the three types of coupling in a multi-stage amplifier.

RC coupling, transformer coupling, direct coupling

Know some advantages and disadvantages of direct-coupled, RC-coupled, and transformer-coupled amplifiers.

RC is cheap but low gain, direct is cheap but can’t amplify high frequencies, transformer has higher gain but has poor frequency response