Mod 4 - penn - Transistors 1 -\
when no voltage at all is con nected to the base, the base bias voltage is zero, or zero base bias. No current will flow through the transistor.
when no voltage at all is con nected to the base, the base bias voltage is zero, or zero base bias. No current will flow through the transistor.
Since the majoritycharge car riers in a PNP transistor are holes, holes enter the device through the emitter and leave through the collector.
Since the majoritycharge car riers in a PNP transistor are holes, holes enter the device through the emitter and leave through the collector.
So, an NPN transistor contains a thin layer of P-type material sandwiched between two thicker sections of N-type material.
So, an NPN transistor contains a thin layer of P-type material sandwiched between two thicker sections of N-type material.
That is, the arrow points toward the N-type material and away from the P-type material.) Or, remember this: the arrow in the symbol for an NPN transistor Never Points iN.
That is, the arrow points toward the N-type material and away from the P-type material.) Or, remember this: the arrow in the symbol for an NPN transistor Never Points iN.
The Mathematical Relationship of Currents in a Transistor
The Mathematical Relationship of Currents in a Transistor
The P-type material is only allowed to grow for a short time; then, the ingot is again doped with donor atoms to turn the ingot back into N-type material. The end result is an ingot containing layers of semiconductor material in the NPN formation
The P-type material is only allowed to grow for a short time; then, the ingot is again doped with donor atoms to turn the ingot back into N-type material. The end result is an ingot containing layers of semiconductor material in the NPN formation
The PNP transistor is just the opposite: it contains a thin layer of N-type material between two layers of P-type material.
The PNP transistor is just the opposite: it contains a thin layer of N-type material between two layers of P-type material.
The ability of a transistor to "magnify" current is called amplification.
The ability of a transistor to "magnify" current is called amplification.
The common-emitter amplifier is the most commonly used amplifier configuration (Figure 19). The input signal is deliv- ered to the base, and the output signal is taken away from the collector. The emitter is common to both the input and output terminals.
The common-emitter amplifier is the most commonly used amplifier configuration (Figure 19). The input signal is deliv- ered to the base, and the output signal is taken away from the collector. The emitter is common to both the input and output terminals.
The flow of current through a transistor is dependent on the relation ship of the base voltage to the emitter-collector voltage. In an NPN transistor, the base voltage is positive with respect to the emitter volt age. In a PNP transistor, the base voltage is negative with respect to the emitter voltage.
The flow of current through a transistor is dependent on the relation ship of the base voltage to the emitter-collector voltage. In an NPN transistor, the base voltage is positive with respect to the emitter volt age. In a PNP transistor, the base voltage is negative with respect to the emitter voltage.
The junction between the emitter and the base is called the emitter-base junction or the E-B junction, and the junction between the base and the collector is called the base-collector junction or the B-C junction
The junction between the emitter and the base is called the emitter-base junction or the E-B junction, and the junction between the base and the collector is called the base-collector junction or the B-C junction
The term gain is used to refer to an amplifier's ability to increase the amplitude of a weak signal. The gain could be a current gain, a volt age gain, or a power gain. Gain is easily calculated by dividing the value of an amplifier's output sig- nal by the value of its input signal.
The term gain is used to refer to an amplifier's ability to increase the amplitude of a weak signal. The gain could be a current gain, a volt age gain, or a power gain. Gain is easily calculated by dividing the value of an amplifier's output sig- nal by the value of its input signal.
The three-layer construction of a transistor causes it to have two PN junctions. Because it has two PN junctions, this type of transistor is called a bipolar transistor
The three-layer construction of a transistor causes it to have two PN junctions. Because it has two PN junctions, this type of transistor is called a bipolar transistor
The three-layer construction of a transistor causes it to have two PN junctions. Because it has two PN junctions, this type of transistor is called a bipolar transistor.
The three-layer construction of a transistor causes it to have two PN junctions. Because it has two PN junctions, this type of transistor is called a bipolar transistor.
The value of alpha is equal to the value of the collector current divided by the value of the emitter current. Thus, alpha is a measure of how much emitter current goes to the collector.
The value of alpha is equal to the value of the collector current divided by the value of the emitter current. Thus, alpha is a measure of how much emitter current goes to the collector.
The value of beta is equal to the collector current divided by the base current. So, beta represents the value of current amplification in a transistor.
The value of beta is equal to the collector current divided by the base current. So, beta represents the value of current amplification in a transistor.
The word transistor is a shortened form of current transferring resistor, and this is a good description of what a transistor does in a circuit
The word transistor is a shortened form of current transferring resistor, and this is a good description of what a transistor does in a circuit
specifications because they in dicate the limits of the transistor you are working with.
specifications because they in dicate the limits of the transistor you are working with.
(In other words, the holes flow toward the negative potential.) Thus, electrons enter the device at the collector and exit at the emitter. This is exactly the opposite of what occurs in an NPN transistor.
(In other words, the holes flow toward the negative potential.) Thus, electrons enter the device at the collector and exit at the emitter. This is exactly the opposite of what occurs in an NPN transistor.
, the capaci tor offers an opposition to current flow called capacitive reactance. Capacitive reactance is represented by the symbol XC and is measured in ohms. Likewise, the inductor opposes the flow of AC current, and that opposition is called inductive reactance. Inductive reactance is rep resented by the symbol XL and is also measured in ohms.
, the capaci tor offers an opposition to current flow called capacitive reactance. Capacitive reactance is represented by the symbol XC and is measured in ohms. Likewise, the inductor opposes the flow of AC current, and that opposition is called inductive reactance. Inductive reactance is rep resented by the symbol XL and is also measured in ohms.
A transistor's current gain is indicated by using two related specifications: alpha () and beta (). The values of alpha and beta can tell you how well a bipolar transistor performs as an amplifier. There are two ways
A transistor's current gain is indicated by using two related specifications: alpha () and beta (). The values of alpha and beta can tell you how well a bipolar transistor performs as an amplifier. There are two ways
A common-emitter amplifier configuration is useful for increasing the amplitude of a signal voltage. This type of amplifier has a high input im pedance, which means that it doesn't require a signal source to deliver a lot of current
A common-emitter amplifier configuration is useful for increasing the amplitude of a signal voltage. This type of amplifier has a high input im pedance, which means that it doesn't require a signal source to deliver a lot of current
A complete transistor can be considered to be a junction. Kirchhoff's current law says that the sum of the currents at any junction must be zero. (The currents could be either negative or positive.) Therefore, if we consider the current that enters a transistor to be positive and the current that leaves a transistor to be negative, we can obtain the fol - lowing equation: IE − IB − IC 0 Note that the voltage on the emitter is considered
A complete transistor can be considered to be a junction. Kirchhoff's current law says that the sum of the currents at any junction must be zero. (The currents could be either negative or positive.) Therefore, if we consider the current that enters a transistor to be positive and the current that leaves a transistor to be negative, we can obtain the fol - lowing equation: IE − IB − IC 0 Note that the voltage on the emitter is considered
A mathematical relationship exists between the currents in a transis tor. The emitter current of a transistor (IE) equals the sum of the base current (IB) and the collector current (IC). This is true in both NPN and PNP transistors. This relationship is illustrated with this formula: IE IB IC
A mathematical relationship exists between the currents in a transis tor. The emitter current of a transistor (IE) equals the sum of the base current (IB) and the collector current (IC). This is true in both NPN and PNP transistors. This relationship is illustrated with this formula: IE IB IC
A transistor is a three-terminal, solid-state, semiconductor component that's used to control the flow of electricity in a circuit
A transistor is a three-terminal, solid-state, semiconductor component that's used to control the flow of electricity in a circuit
A transistor's parameters are fixed specifications that tell you what the transistor is capable of doing
A transistor's parameters are fixed specifications that tell you what the transistor is capable of doing
An AC input signal delivered to the base is continually changing in amplitude. This produces the small changes in base current that result in large collector current changes. These changes in base current and collector current are the basic principle behind transistor amplifier operation.
An AC input signal delivered to the base is continually changing in amplitude. This produces the small changes in base current that result in large collector current changes. These changes in base current and collector current are the basic principle behind transistor amplifier operation.
An ohmmeter can be used to test bipolar transistors. An ohmmeter test will tell you whether the transistor you're testing is an NPN or a PNP, and also whether or not the transistor is good.
An ohmmeter can be used to test bipolar transistors. An ohmmeter test will tell you whether the transistor you're testing is an NPN or a PNP, and also whether or not the transistor is good.
Another way to obtain a positive bias voltage on the base of a transis tor is voltage divider biasing (Figure 10). Voltage divider biasing is the most common method of biasing used in transistor circuits.
Another way to obtain a positive bias voltage on the base of a transis tor is voltage divider biasing (Figure 10). Voltage divider biasing is the most common method of biasing used in transistor circuits.
BIPOLAR TRANSISTORS page 1
BIPOLAR TRANSISTORS page 1
Because a small change in the base current produces a relatively large change in the collector current, bipolar transistors can amplify (increase) signals. This is true for both NPN and PNP transistors.
Because a small change in the base current produces a relatively large change in the collector current, bipolar transistors can amplify (increase) signals. This is true for both NPN and PNP transistors.
Because the P sections in a PNP transistor are much larger than the N section, a PNP transistor contains many more holes than electrons. Thus, in a PNP transistor, the majority-charge carri - ers are holes and the minority charge carriers are electrons
Because the P sections in a PNP transistor are much larger than the N section, a PNP transistor contains many more holes than electrons. Thus, in a PNP transistor, the majority-charge carri - ers are holes and the minority charge carriers are electrons
Because the P sections in a PNP transistor are much larger than the N section, a PNP transistor contains many more holes than electrons. Thus, in a PNP transistor, the majority-charge carri - ers are holes and the minority charge carriers are electrons.
Because the P sections in a PNP transistor are much larger than the N section, a PNP transistor contains many more holes than electrons. Thus, in a PNP transistor, the majority-charge carri - ers are holes and the minority charge carriers are electrons.
Bipolar Transistor Construction
Bipolar Transistor Construction
FIELD-EFFECT TRANSISTORS (FETS)
FIELD-EFFECT TRANSISTORS (FETS)
First Study file on Transistors
First Study file on Transistors
If a small cu rent is applied to the input terminals of a transistor, a magnified current will appear at the output terminals.
If a small cu rent is applied to the input terminals of a transistor, a magnified current will appear at the output terminals.
If the base current is set to a point where the collector cur- rent is at a maximum or minimum value, half of the output signal will be lost. That is, distortion will occur in the output signal. However, note that it's sometimes desirable to operate the transistor this way.
If the base current is set to a point where the collector cur- rent is at a maximum or minimum value, half of the output signal will be lost. That is, distortion will occur in the output signal. However, note that it's sometimes desirable to operate the transistor this way.
If the value of an amplifier's output signal is less than the value of the input signal, the gain is less than 1.0. Note that the voltage gain in a common-collector amplifier is always less than 1.0. Thus, there's a de crease in signal voltage amplitude as it passes through the amplifier.
If the value of an amplifier's output signal is less than the value of the input signal, the gain is less than 1.0. Note that the voltage gain in a common-collector amplifier is always less than 1.0. Thus, there's a de crease in signal voltage amplitude as it passes through the amplifier.
If we continue to raise the base current, a point will be reached where the collector current levels off. This is called the saturation point; at that point, the transistor is conducting as much current as it can.
If we continue to raise the base current, a point will be reached where the collector current levels off. This is called the saturation point; at that point, the transistor is conducting as much current as it can.
If you increase the base current (by making the base voltage more positive in NPN transistors or more negative in PNP transistors), more charge carriers are pulled into the base region, where they fall under the influence of the collector field. Therefore, a small increase in the number of charge carriers that enter the base region results in a larger collector current.
If you increase the base current (by making the base voltage more positive in NPN transistors or more negative in PNP transistors), more charge carriers are pulled into the base region, where they fall under the influence of the collector field. Therefore, a small increase in the number of charge carriers that enter the base region results in a larger collector current.
In a linear amplifier, the positive and negative swings of the output current waveform are amplified equally. In a nonlinear amplifier, certain portions of the signal are more amplified than others
In a linear amplifier, the positive and negative swings of the output current waveform are amplified equally. In a nonlinear amplifier, certain portions of the signal are more amplified than others
In a transistor, the emitter is considered to be the entry port for the charge carriers. So, in an NPN transistor, electrons enter at the emitter. The collector is the exit port (the place where most of the electrons leave the device). The base is the control electrode, or control port. Its job is to control the number of electrons that pass through the transistor on their way from the emitter to the collector
In a transistor, the emitter is considered to be the entry port for the charge carriers. So, in an NPN transistor, electrons enter at the emitter. The collector is the exit port (the place where most of the electrons leave the device). The base is the control electrode, or control port. Its job is to control the number of electrons that pass through the transistor on their way from the emitter to the collector
In basic terms, a transistor is made from three layers of doped semi conductor crystals (usually silicon or germanium). These three layers of N-type and P-type semiconductor crystals are arranged in either an NPN formation or a PNP formation
In basic terms, a transistor is made from three layers of doped semi conductor crystals (usually silicon or germanium). These three layers of N-type and P-type semiconductor crystals are arranged in either an NPN formation or a PNP formation
In each type of transistor, the entire sandwich of semiconductor material is enclosed in a protective plastic or metal case, and electrical contacts and leads are attached to each of the three layers an NPN transistor
In each type of transistor, the entire sandwich of semiconductor material is enclosed in a protective plastic or metal case, and electrical contacts and leads are attached to each of the three layers an NPN transistor
In order to get a bipolar transistor into operation, a voltage must be ap plied to both the base and the collector. However, a transistor is actually considered to be a current-operated device, because a small change in base current results in a very large change in collector current.
In order to get a bipolar transistor into operation, a voltage must be ap plied to both the base and the collector. However, a transistor is actually considered to be a current-operated device, because a small change in base current results in a very large change in collector current.
In the NPN transistor, the P section is called the base. One N section is called the emitter, and the other N section is called the collector. Note that in most NPN transistors, the emitter layer is thinner than the collector layer.
In the NPN transistor, the P section is called the base. One N section is called the emitter, and the other N section is called the collector. Note that in most NPN transistors, the emitter layer is thinner than the collector layer.
In the PNP transistor, the collector and emitter regions are P-type ma terial and the base is N-type material. As with the NPN type, the base of the PNP transistor is very thin. Remember that an N-type semi conductor material contains extra electrons and a P-type semiconductor material contains extra holes.
In the PNP transistor, the collector and emitter regions are P-type ma terial and the base is N-type material. As with the NPN type, the base of the PNP transistor is very thin. Remember that an N-type semi conductor material contains extra electrons and a P-type semiconductor material contains extra holes.
In the PNP transistor, the collector and emitter regions are P-type ma terial and the base is N-type material. As with the NPN type, the base of the PNP transistor is very thin. Remember that an N-type semiconductor material contains extra electrons and a P-type semiconductor material contains extra holes.
In the PNP transistor, the collector and emitter regions are P-type ma terial and the base is N-type material. As with the NPN type, the base of the PNP transistor is very thin. Remember that an N-type semiconductor material contains extra electrons and a P-type semiconductor material contains extra holes.
In the schematic symbol for the NPN transistor, the letters E, B, and C are used to label the emitter, base, and collector leads. If these letters aren't used to identify the leads, just remember that the arrow always identifies the emitter.
In the schematic symbol for the NPN transistor, the letters E, B, and C are used to label the emitter, base, and collector leads. If these letters aren't used to identify the leads, just remember that the arrow always identifies the emitter.
NPN -- Remember also that the arrow points in the direction of positive-to-negative conventional current flow through the transistor, and against the negative-to-positive flow of electron current.
NPN -- Remember also that the arrow points in the direction of positive-to-negative conventional current flow through the transistor, and against the negative-to-positive flow of electron current.
NPN--remember that the arrow always identifies the emitter. (That is, the arrow points toward the N-type material and away from the P-type material.) Or, remember this: the arrow in the symbol for an NPN transistor Never Points iN
NPN -- remember that the arrow always identifies the emitter. (That is, the arrow points toward the N-type material and away from the P-type material.) Or, remember this: the arrow in the symbol for an NPN transistor Never Points iN
NPN transistor -
NPN transistor -
Note that a few electrons are attracted to the positive base lead. However, since the collector lead is much more positive than the base lead, only a small amount of the electrons are attracted to the base. In all, about 98 percent of the electrons pass through the collector lead, and the remaining 2 percent pass through the base lead.
Note that a few electrons are attracted to the positive base lead. However, since the collector lead is much more positive than the base lead, only a small amount of the electrons are attracted to the base. In all, about 98 percent of the electrons pass through the collector lead, and the remaining 2 percent pass through the base lead.
Note that if the base current continues to rise past the transistor's saturation point, there will actually be a reduction in amplification. The output signal will be distorted; that is, the output waveform won't have the same shape as the input waveform. When too much current is delivered to a transistor, the transistor is said to be operat ing in overdrive. Overdrive causes inefficiency in a circuit, and the transistor could be destroyed.
Note that if the base current continues to rise past the transistor's saturation point, there will actually be a reduction in amplification. The output signal will be distorted; that is, the output waveform won't have the same shape as the input waveform. When too much current is delivered to a transistor, the transistor is said to be operat ing in overdrive. Overdrive causes inefficiency in a circuit, and the transistor could be destroyed.
Note that some volt-ohm-milliammeters (VOMs) can deliver a very high current when the ohmmeter is in the R 1 position. Therefore, avoid using the R 1 ohmmeter scale when making any ohmmeter measurements on a PN junction. Also, avoid using the R 10 k or R 100 k scales, as they may use a higher ohmmeter voltage power supply
Note that some volt-ohm-milliammeters (VOMs) can deliver a very high current when the ohmmeter is in the R 1 position. Therefore, avoid using the R 1 ohmmeter scale when making any ohmmeter measurements on a PN junction. Also, avoid using the R 10 k or R 100 k scales, as they may use a higher ohmmeter voltage power supply
Note that the construction of a transistor is similar to that of a diode. However, a diode has only one PN junction, while a transistor has two junctions
Note that the construction of a transistor is similar to that of a diode. However, a diode has only one PN junction, while a transistor has two junctions
Note that the voltage on the emitter is considered to be 0 V with re spect to the voltages on the base and collector. You'll find that this is the characteristic way of representing voltages in amplifying devices. For example, in a field effect transistor, the source (which is roughly equal to the cathode of a vacuum tube) is considered to be 0 V with reference to the other electrodes in the device.
Note that the voltage on the emitter is considered to be 0 V with re spect to the voltages on the base and collector. You'll find that this is the characteristic way of representing voltages in amplifying devices. For example, in a field effect transistor, the source (which is roughly equal to the cathode of a vacuum tube) is considered to be 0 V with reference to the other electrodes in the device.
Note: When you're troubleshooting a transistor circuit, you must learn to treat the DC and AC voltages separately, even though those voltages are on the same electrodes at the same time!
Note: When you're troubleshooting a transistor circuit, you must learn to treat the DC and AC voltages separately, even though those voltages are on the same electrodes at the same time!
Operation of a PNP Transistor
Operation of a PNP Transistor
Page 3In a PNP transistor, the N section is the base, while the emitter and collector are made of P-type material
Page 3In a PNP transistor, the N section is the base, while the emitter and collector are made of P-type material
Page 4
Page 4
Page 4 - 5 In order to get a transistor operating, a DC voltage or current must be applied to the base lead of the transistor. Applying the needed DC potentials to the electrodes of a transistor in order to "push" the transistor into conduction is called biasing.
Page 4 - 5 In order to get a transistor operating, a DC voltage or current must be applied to the base lead of the transistor. Applying the needed DC potentials to the electrodes of a transistor in order to "push" the transistor into conduction is called biasing.
Page 4 Operation of an NPN Transistor Remember that an N-type semiconductor material contains extra electrons and a P-type semiconductor material contains extra holes (spaces for electrons). Because the P section is much smaller than the N sections in an NPN transistor, the transistor contains many more extra electrons than holes. Thus, in an NPN transistor, the majority-charge carriers are electrons and the minority charge carriers are holes.
Page 4 Operation of an NPN Transistor Remember that an N-type semiconductor material contains extra electrons and a P-type semiconductor material contains extra holes (spaces for electrons). Because the P section is much smaller than the N sections in an NPN transistor, the transistor contains many more extra electrons than holes. Thus, in an NPN transistor, the majority-charge carriers are electrons and the minority charge carriers are holes.
Penn Foster Mod 4 - Transistor
Penn Foster Mod 4 - Transistor
Power Supply Biasing
Power Supply Biasing
Remember also that the arrow points in the direction of positive-to-negative conventional current flow through the transistor, and against the negative-to-positive flow of electron current.
Remember also that the arrow points in the direction of positive-to-negative conventional current flow through the transistor, and against the negative-to-positive flow of electron current.
Remember that the base is the control electrode in a transistor. The base controls the flow of electrons as they pass through the transistor from the emitter to the collector
Remember that the base is the control electrode in a transistor. The base controls the flow of electrons as they pass through the transistor from the emitter to the collector
Remember that the majority-charge carriers enter a transistor at the emitter and leave through the collector
Remember that the majority-charge carriers enter a transistor at the emitter and leave through the collector
Remember that the majority-charge carriers enter a transistor at the emitter and leave through the collector. Since the majoritycharge car riers in a PNP transistor are holes, holes enter the device through the emitter and leave through the collector.
Remember that the majority-charge carriers enter a transistor at the emitter and leave through the collector. Since the majoritycharge car riers in a PNP transistor are holes, holes enter the device through the emitter and leave through the collector.
Remember, you must always consider the DC and AC voltages in an amplifier circuit separately, even though the two voltages appear on an ampli fier terminal at the same time!
Remember, you must always consider the DC and AC voltages in an amplifier circuit separately, even though the two voltages appear on an ampli fier terminal at the same time!
Thus, the value of the base current greatly affects the operation of a transistor. By adjusting the value of the base current, the bias point of the transistor is changed and the output signal is varied. In most amplifiers, the DC base current sets the collector current at some point midway between the possible minimum and maximum values. That way, the output signal has the same shape as the input signal, containing the full positive and negative swings of the input signal. Under these conditions, a transistor is operating most efficiently (Figure 6).
Thus, the value of the base current greatly affects the operation of a transistor. By adjusting the value of the base current, the bias point of the transistor is changed and the output signal is varied. In most amplifiers, the DC base current sets the collector current at some point midway between the possible minimum and maximum values. That way, the output signal has the same shape as the input signal, containing the full positive and negative swings of the input signal. Under these conditions, a transistor is operating most efficiently (Figure 6).
To test a transistor for a short or open, you'll need to perform three separate resistance measurements: base to emitter, base to collector, and emitter to collector. This process is the same for both NPN and PNP transistors; however, the readings will be reversed for the two types.
To test a transistor for a short or open, you'll need to perform three separate resistance measurements: base to emitter, base to collector, and emitter to collector. This process is the same for both NPN and PNP transistors; however, the readings will be reversed for the two types.
Transistor Biasing In a
Transistor Biasing In a
When only a DC signal is connected to a transistor, the tran- sistor is said to be in the static mode of operation. When an AC input signal is applied, the transistor is said to be in the dynamic mode of operation
When only a DC signal is connected to a transistor, the tran- sistor is said to be in the static mode of operation. When an AC input signal is applied, the transistor is said to be in the dynamic mode of operation
When you're studying what goes on inside the PNP transistor, you should think of holes flowing from the emitter to the collector and from the emitter to the base. Most of the holes that enter into the base fall under the influence of the highly negative collector potential. Thus, more than 98 percent of the holes go to the collector and only about 2 percent go to the base.
When you're studying what goes on inside the PNP transistor, you should think of holes flowing from the emitter to the collector and from the emitter to the base. Most of the holes that enter into the base fall under the influence of the highly negative collector potential. Thus, more than 98 percent of the holes go to the collector and only about 2 percent go to the base.
an NPN transistor is grown in a laboratory from a single piece of semiconductor material. The piece of semi conductor material is called an ingot. As the ingot begins to grow, it's doped with donor atoms to make it into N-type material. When the ingot is about half way grown, the dopant is changed to acceptor atoms turning the ingot into P-type material at that point. page 2
an NPN transistor is grown in a laboratory from a single piece of semiconductor material. The piece of semi conductor material is called an ingot. As the ingot begins to grow, it's doped with donor atoms to make it into N-type material. When the ingot is about half way grown, the dopant is changed to acceptor atoms turning the ingot into P-type material at that point. page 2