ITEC 320 Test #2 Flashcards
Transistor
A solid-state device made of semiconductor material such as silicon or germanium.
Types of transistors
NPN and PNP
Three elements of a transistor
Base, emitter, and collector
Base
Inner element of a transistor. The base controls transistor action.
What material is the base made out of in a NPN transistor
P material
What material is the base made out of in a PNP transistor
N material
Emitter
On of the outer elements of the transistor
What material is the emitter made out of in a NPN transistor
N material
What material is the emitter made out of in a PNP transistor
P material
Collector
One of the other outer elements of a transistor
What material is the collector made out of in a NPN transistor
N material
What material is the collector made out of in a PNP transistor
P material
NPN transistor
A bipolar transistor in which outer elements (emitter and collector) are made of N-type of semiconductor material and the inner element (base) is made out of P-type material
PNP transistor
A bipolar transistor in which the outer elements (emitter and collector) are made out of P-type semiconductor material and the inner element (base) is made out of N-type material
P-type material
Semiconductor material that is doped with very small amounts of acceptor impurity materials that decrease active electrons.
What are the majority charge carriers in P-type materials
Holes
N-type material
Semiconductor material that is doped with very small amounts of donor impurity materials that add active electrons.
What are the majority charge carriers in N-type materials
Electrons
What are 2 basic transistor types
NPN and PNP
How many elements does a transistor have
3 (base , emitter, and collector)
In the transistor schematic symbol, the arrow is on what element
Emitter
What is the most common problem with transistors
Overheating
What can you use in place of a transistor tester to check transistors
Ohmmeter
When reverse biased, a diode will block, pass current
Block
When forward biased, a diode will block, pass current
Pass
When testing transistors, consider them to be
Back-to-back diodes
A diode that is forward biased will have high, low resistance
Low
A diode that is reverse biased will have high, infinity resistance
Infinity
To test transistors to determine if they are NPN or PNP, what must you know about the ohmmeter
The negative and positive leads
The positive probe is on what material when a diode is reverse biased
Cathode (-)
The negative probe is on what material when a diode is reversed biased
Anode (+)
A reverse-biased junction will show what resistance reading
0.2
When a component is being tested with an ohmmeter, it is usually in series, parrallel with the internal supply voltage
Series
In a transistor, a smaller what controls the larger currents
Base
A NPN transistor consists of
A layer or P-type material between two layers of N-type material
A common transistor problem is
Shorted transistor
Transistors are
Reliable, but destructible
If both the forward and reverse emitter-base resistances are low, then the transistor is
Shortened
When testing transistors, you can consider them to be
Back-to-back diodes
When a diode is forward biased, it is indicating a
Low resistance
How can you indicate which leads of a transistor are P-type and which are N-type using an ohmmeter
Polarity
In what device does a small amount of current control a large amount of current
Transistor
What current determines the amount of collector current
Base current
Does an increase in base current cause a decrease in collector current
No
Does the resistance of a transistor increase or decrease with an increase of base current
Decreases
Common base
A transistor circuit where the base is common (circuit ground) to the input and output signals. This circuit does not produce a phase shift
Common emitter
A transistor circuit where the emitter is common (circuit ground) to the input and output signals. This circuit produces a 180 degree phase shift
Common collector
A transistor circuit where the collector is common to the input and output signals. Collector is usually an AC ground. This circuit does not produce a phase shift
Regardless of the circuit arrangement used, the transistor-emitter base junction must always be what bias
Forward
In the common-collector circuit, the input signal is applied between……….and…………regions of the transistor
Base and emitter
Does the common-collector circuit provide an output voltage greater than its input voltage
No losses 1/10 volt
Does a common-emitter circuit use the same bias polarities in PNP and NPN circuits
No
Is the input signal to a common-emitter circuit 180 degrees out of phase with the output signal
Yes
Transistor power rating
The max power that a transistor can dissipate without damage to it.
Transistor power rating equation
P = VCE x IC
Can you operate transistors under a wide variety of operating voltages and currents
Yes, because it is all about how they are biased. They can’t exceed their current handling or voltage drop
What is the max amount of power a transistor can dissipate called
Power rating
What results when you exceed the max power specifications of a transistor
Damage to the transistor
Base current (IB), is the amount that will pass from
Emitter to base
The base-to-emitter current, in effect, controls the
Collector current
For current control to take place
A transistor must be properly biased
For forward biasing, The P-type base material in an NPN transistor must be what with respect to the N-type emitter material
Positive
In use, the emitter-base voltage is usually taken from the
Collector supply
When a circuit increases its AC input signal to a greater amplitude, it has
Gain
In a common-base circuit
The base is common to both the input and output signals
The common-collector circuit is often used as a
Impedance-matching device
Energy a transistor receives when operating in a circuit is transferred as
Dissipated heat
Voltage regulation
The process of maintaining the output voltage a power source constant with respect to changes of input voltage and loading.
Voltage regulator
A circuit or device that minimizes the changes of output voltage of a power supply as the load on the supply varied
Percentage of regulation
The percentage by which a power supply voltage changes when a load is applied compared with full-load voltage
Shunt regulator
A variable device connected across the load terminals of a regulated power supply. Its resistance automatically varies the voltage across a series resistor. The resulting action maintains the load voltage at a constant level.
Series voltage regulator
A voltage regulator that uses an automatically variable resistance in series with the load to control the output voltage
Voltage regulator circuits are used to
Filter circuits and refine the filtering process
Voltage regulator circuits provide voltage regulation for
Power supplies
In a power source, each component adds up to
An internal resistance in series with the output current
What diode is an effective shunt regulator
Zener
Voltage output changes can occur because of a variation in
Line voltage input
The smaller the percentage of regulation
The better the regulator
In a shunt voltage regulator, the regulator acts as an
Resistance in parallel to the load
In a series voltage regulator, the regulator acts as an
Resistance in series with the load
One use of a series voltage regulator is as an
Ripple filter
An increase in current will cause the series regulator to
Decrease in resistance
Gain
The ratio of output signal amplitude of an amplifier to its input signal amplitude. Expressed in terms of voltage, current, or power. Can also be expressed in decibels.
Characterisitc curve
A graph showing the relationship between changing values, voltage, and current
Gain formula
Gain = output voltage / input voltage
Amplifier
A group of electronic components connected in such a way as to increase the strength of an electrical signal applied to its input
What does gain determine
The amount of amplification an amplifier can provide
Amplifiers increase current and
Voltage
Are amplifiers used to operate in different frequencies
Yes
Cascaded amplifiers
Two or more amplifiers connected one after another. The output of the first amplifier supplies the signal to the input of the second amplifier
How do you obtain large gains
Cascaded amplifiers
How do you determine the total gain of amplifiers in cascade
Multiplying the product of their individual gains
A set of characteristic curves show the relationship between
Base current and collector current
Each individual curve represents
A different emitter bias current
The vertical axis of the graph represents
Collector current
The horizontal axis of the graph represents
Collector voltage
For what can you use a set of characteristic curves
Find the operating range of the transistor
What is the best source for a specification sheet of a particular device
Manufacturer
What is the danger of exceeding maximum ratings
Overheating or damage
When looking at a specification sheet, how do you determine which specifications are of the greater importance
Always on the first page and labeled maximum
Can a transistor lead-out be found on a specification sheet
Yes
An amplifier is a circuit that increases the amplitude of a
Alternating waveform
To determine how much an amplifier can increase a signal, you determine
Gain
Amplifiers may amplify either
Current or voltage
Amplifiers that amplify both current and voltage are called
Power amps
When you need large gains, you can connect
Cascaded amplifiers
The total gain of two amplifiers connected in cascade is
The product of their individual gains
