Electronic components are classed into either being Passive devices or Active devices. Active devices are different from passive devices. These devices are capable of changing their operational performance, may deliver power to the circuit, and can perform interesting mathematical functions. While a device that does not require a source of energy for its operation.
What are Active Devices?
An active device is any type of circuit component with the ability to electrically control electron flow (electricity controlling electricity). In order for a circuit to be properly called electronic, it must contain at least one active device. Active devices include, but are not limited to, vacuum tubes, transistors, silicon-controlled rectifiers (SCRs), and TRIACs.
All active devices control the flow of electrons through them. Some active devices allow a voltage to control this current while other active devices allow another current to do the job. Devices utilizing a static voltage as the controlling signal are, not surprisingly, called voltage-controlled devices. Devices working on the principle of one current controlling another current are known as current-controlled devices. For the record, vacuum tubes are voltage-controlled devices while transistors are made as either voltage-controlled or current controlled types. The first type of transistor successfully demonstrated was a current-controlled device.
-------------------------------------------------------------------
Electronic components are classed into either being Passive devices or Active devices. Active devices are different from passive devices. These devices are capable of changing their operational performance, may deliver power to the circuit, and can perform interesting mathematical functions. While a device that does not require a source of energy for its operation.
What are Active Devices?
An active device is any type of circuit component with the ability to electrically control electron flow (electricity controlling electricity). In order for a circuit to be properly called electronic, it must contain at least one active device. Active devices include, but are not limited to, vacuum tubes, transistors, silicon-controlled rectifiers (SCRs), and TRIACs.
All active devices control the flow of electrons through them. Some active devices allow a voltage to control this current while other active devices allow another current to do the job. Devices utilizing a static voltage as the controlling signal are, not surprisingly, called voltage-controlled devices. Devices working on the principle of one current controlling another current are known as current-controlled devices. For the record, vacuum tubes are voltage-controlled devices while transistors are made as either voltage-controlled or current controlled types. The first type of transistor successfully demonstrated was a current-controlled device.
-------------------------------------------------------
Electronic components are classed into either being Passive devices or Active devices. Active devices are different from passive devices. These devices are capable of changing their operational performance, may deliver power to the circuit, and can perform interesting mathematical functions. While a device that does not require a source of energy for its operation.
What are Active Devices?
An active device is any type of circuit component with the ability to electrically control electron flow (electricity controlling electricity). In order for a circuit to be properly called electronic, it must contain at least one active device. Active devices include, but are not limited to, vacuum tubes, transistors, silicon-controlled rectifiers (SCRs), and TRIACs.
All active devices control the flow of electrons through them. Some active devices allow a voltage to control this current while other active devices allow another current to do the job. Devices utilizing a static voltage as the controlling signal are, not surprisingly, called voltage-controlled devices. Devices working on the principle of one current controlling another current are known as current-controlled devices. For the record, vacuum tubes are voltage-controlled devices while transistors are made as either voltage-controlled or current controlled types. The first type of transistor successfully demonstrated was a current-controlled device.
-----------------------------------------------------------------
Field Effect Transistor
In the Bipolar Junction Transistor tutorials, we saw that the output Collector current is determined by the amount of current flowing into the Base terminal of the device and thereby making the Bipolar Transistor a CURRENT operated device. The Field Effect Transistor, or simply FET however, use the voltage that is applied to their input terminal to control the output current, since their operation relies on the electric field (hence the name field effect) generated by the input voltage. This then makes the Field Effect Transistor a VOLTAGE operated device.
The Field Effect Transistor is a unipolar device that has very similar properties to those of the Bipolar Transistor ie, high efficiency, instant operation, robust and cheap, and they can be used in most circuit applications that use the equivalent Bipolar Junction Transistors, (BJT). They can be made much smaller than an equivalent BJT transistor and along with their low power consumption and dissipation make them ideal for use in integrated circuits such as the CMOS range of chips.
We remember from the previous tutorials that there are two basic types of Bipolar Transistor construction,NPN and PNP, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. There are also two basic types of Field Effect Transistor, N-channel and P-channel. As their name implies, Bipolar Transistors are "Bipolar" devices because they operate with both types of charge carriers, Holes and Electrons. The Field Effect Transistor on the other hand is a "Unipolar" device that depends only on the conduction of Electrons (N-channel) or Holes (P-channel).
The Field Effect Transistor has one major advantage over its standard bipolar transistor cousins, in that their input impedance is very high, (Thousands of Ohms) making them very sensitive to input signals, but this high sensitivity also means that they can be easily damaged by static electricity. There are two main types of field effect transistor, the Junction Field Effect Transistor or JFET and the Insulated-gate Field Effect Transistor or IGFET), which is more commonly known as the standard Metal Oxide Semiconductor Field Effect Transistor or MOSFET for short.
--------------------------------------------------------------
Field Effect Transistor
In the Bipolar Junction Transistor tutorials, we saw that the output Collector current is determined by the amount of current flowing into the Base terminal of the device and thereby making the Bipolar Transistor a CURRENT operated device. The Field Effect Transistor, or simply FET however, use the voltage that is applied to their input terminal to control the output current, since their operation relies on the electric field (hence the name field effect) generated by the input voltage. This then makes the Field Effect Transistor a VOLTAGE operated device.
The Field Effect Transistor is a unipolar device that has very similar properties to those of the Bipolar Transistor ie, high efficiency, instant operation, robust and cheap, and they can be used in most circuit applications that use the equivalent Bipolar Junction Transistors, (BJT). They can be made much smaller than an equivalent BJT transistor and along with their low power consumption and dissipation make them ideal for use in integrated circuits such as the CMOS range of chips.
We remember from the previous tutorials that there are two basic types of Bipolar Transistor construction,NPN and PNP, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. There are also two basic types of Field Effect Transistor, N-channel and P-channel. As their name implies, Bipolar Transistors are "Bipolar" devices because they operate with both types of charge carriers, Holes and Electrons. The Field Effect Transistor on the other hand is a "Unipolar" device that depends only on the conduction of Electrons (N-channel) or Holes (P-channel).
The Field Effect Transistor has one major advantage over its standard bipolar transistor cousins, in that their input impedance is very high, (Thousands of Ohms) making them very sensitive to input signals, but this high sensitivity also means that they can be easily damaged by static electricity. There are two main types of field effect transistor, the Junction Field Effect Transistor or JFET and the Insulated-gate Field Effect Transistor or IGFET), which is more commonly known as the standard Metal Oxide Semiconductor Field Effect Transistor or MOSFET for short.
--------------------------------------------------------------------------------------------------------------------------
Field Effect Transistor
In the Bipolar Junction Transistor tutorials, we saw that the output Collector current is determined by the amount of current flowing into the Base terminal of the device and thereby making the Bipolar Transistor a CURRENT operated device. The Field Effect Transistor, or simply FET however, use the voltage that is applied to their input terminal to control the output current, since their operation relies on the electric field (hence the name field effect) generated by the input voltage. This then makes the Field Effect Transistor a VOLTAGE operated device.
The Field Effect Transistor is a unipolar device that has very similar properties to those of the Bipolar Transistor ie, high efficiency, instant operation, robust and cheap, and they can be used in most circuit applications that use the equivalent Bipolar Junction Transistors, (BJT). They can be made much smaller than an equivalent BJT transistor and along with their low power consumption and dissipation make them ideal for use in integrated circuits such as the CMOS range of chips.
We remember from the previous tutorials that there are two basic types of Bipolar Transistor construction,NPN and PNP, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. There are also two basic types of Field Effect Transistor, N-channel and P-channel. As their name implies, Bipolar Transistors are "Bipolar" devices because they operate with both types of charge carriers, Holes and Electrons. The Field Effect Transistor on the other hand is a "Unipolar" device that depends only on the conduction of Electrons (N-channel) or Holes (P-channel).
The Field Effect Transistor has one major advantage over its standard bipolar transistor cousins, in that their input impedance is very high, (Thousands of Ohms) making them very sensitive to input signals, but this high sensitivity also means that they can be easily damaged by static electricity. There are two main types of field effect transistor, the Junction Field Effect Transistor or JFET and the Insulated-gate Field Effect Transistor or IGFET), which is more commonly known as the standard Metal Oxide Semiconductor Field Effect Transistor or MOSFET for short.
----------------------------------------------------------------------------------------------------------------------------------
Field Effect Transistor
In the Bipolar Junction Transistor tutorials, we saw that the output Collector current is determined by the amount of current flowing into the Base terminal of the device and thereby making the Bipolar Transistor a CURRENT operated device. The Field Effect Transistor, or simply FET however, use the voltage that is applied to their input terminal to control the output current, since their operation relies on the electric field (hence the name field effect) generated by the input voltage. This then makes the Field Effect Transistor a VOLTAGE operated device.
The Field Effect Transistor is a unipolar device that has very similar properties to those of the Bipolar Transistor ie, high efficiency, instant operation, robust and cheap, and they can be used in most circuit applications that use the equivalent Bipolar Junction Transistors, (BJT). They can be made much smaller than an equivalent BJT transistor and along with their low power consumption and dissipation make them ideal for use in integrated circuits such as the CMOS range of chips.
We remember from the previous tutorials that there are two basic types of Bipolar Transistor construction,NPN and PNP, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. There are also two basic types of Field Effect Transistor, N-channel and P-channel. As their name implies, Bipolar Transistors are "Bipolar" devices because they operate with both types of charge carriers, Holes and Electrons. The Field Effect Transistor on the other hand is a "Unipolar" device that depends only on the conduction of Electrons (N-channel) or Holes (P-channel).
The Field Effect Transistor has one major advantage over its standard bipolar transistor cousins, in that their input impedance is very high, (Thousands of Ohms) making them very sensitive to input signals, but this high sensitivity also means that they can be easily damaged by static electricity. There are two main types of field effect transistor, the Junction Field Effect Transistor or JFET and the Insulated-gate Field Effect Transistor or IGFET), which is more commonly known as the standard Metal Oxide Semiconductor Field Effect Transistor or MOSFET for short.
--------------------------------------------------------------------
Field Effect Transistor
In the Bipolar Junction Transistor tutorials, we saw that the output Collector current is determined by the amount of current flowing into the Base terminal of the device and thereby making the Bipolar Transistor a CURRENT operated device. The Field Effect Transistor, or simply FET however, use the voltage that is applied to their input terminal to control the output current, since their operation relies on the electric field (hence the name field effect) generated by the input voltage. This then makes the Field Effect Transistor a VOLTAGE operated device.
The Field Effect Transistor is a unipolar device that has very similar properties to those of the Bipolar Transistor ie, high efficiency, instant operation, robust and cheap, and they can be used in most circuit applications that use the equivalent Bipolar Junction Transistors, (BJT). They can be made much smaller than an equivalent BJT transistor and along with their low power consumption and dissipation make them ideal for use in integrated circuits such as the CMOS range of chips.
We remember from the previous tutorials that there are two basic types of Bipolar Transistor construction,NPN and PNP, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. There are also two basic types of Field Effect Transistor, N-channel and P-channel. As their name implies, Bipolar Transistors are "Bipolar" devices because they operate with both types of charge carriers, Holes and Electrons. The Field Effect Transistor on the other hand is a "Unipolar" device that depends only on the conduction of Electrons (N-channel) or Holes (P-channel).
The Field Effect Transistor has one major advantage over its standard bipolar transistor cousins, in that their input impedance is very high, (Thousands of Ohms) making them very sensitive to input signals, but this high sensitivity also means that they can be easily damaged by static electricity. There are two main types of field effect transistor, the Junction Field Effect Transistor or JFET and the Insulated-gate Field Effect Transistor or IGFET), which is more commonly known as the standard Metal Oxide Semiconductor Field Effect Transistor or MOSFET for short.
----------------------------------------------------------------------------------------
Field Effect Transistor
In the Bipolar Junction Transistor tutorials, we saw that the output Collector current is determined by the amount of current flowing into the Base terminal of the device and thereby making the Bipolar Transistor a CURRENT operated device. The Field Effect Transistor, or simply FET however, use the voltage that is applied to their input terminal to control the output current, since their operation relies on the electric field (hence the name field effect) generated by the input voltage. This then makes the Field Effect Transistor a VOLTAGE operated device.
The Field Effect Transistor is a unipolar device that has very similar properties to those of the Bipolar Transistor ie, high efficiency, instant operation, robust and cheap, and they can be used in most circuit applications that use the equivalent Bipolar Junction Transistors, (BJT). They can be made much smaller than an equivalent BJT transistor and along with their low power consumption and dissipation make them ideal for use in integrated circuits such as the CMOS range of chips.
We remember from the previous tutorials that there are two basic types of Bipolar Transistor construction,NPN and PNP, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. There are also two basic types of Field Effect Transistor, N-channel and P-channel. As their name implies, Bipolar Transistors are "Bipolar" devices because they operate with both types of charge carriers, Holes and Electrons. The Field Effect Transistor on the other hand is a "Unipolar" device that depends only on the conduction of Electrons (N-channel) or Holes (P-channel).
The Field Effect Transistor has one major advantage over its standard bipolar transistor cousins, in that their input impedance is very high, (Thousands of Ohms) making them very sensitive to input signals, but this high sensitivity also means that they can be easily damaged by static electricity. There are two main types of field effect transistor, the Junction Field Effect Transistor or JFET and the Insulated-gate Field Effect Transistor or IGFET), which is more commonly known as the standard Metal Oxide Semiconductor Field Effect Transistor or MOSFET for short.
---------------------------------------------------------------------------------
Varactor Theory
A varactor is also known as a variable capacitance diode or a varicap. It provides an electrically controllable capacitance, which can be used in tuned circuits. It is small and inexpensive, which makes its use advantageous in many applications. Its disadvantages compared to a manually controlled variable capacitor are a lower Q, nonlinearity, lower voltage rating and a more limited range. Background material on varactors can be found in the Reference.
Any PN junction has a junction capacitance that is a function of the voltage across the junction, as discussed in any account of PN junctions. The electric field in the depletion layer that is set up by the ionized donors and acceptors is responsible for the voltage difference that balances the applied voltage. A higher reverse bias widens the depletion layer, uncovering more fixed charge and raising the junction potential. The capacitance of the junction is C = Q(V)/V, and the incremental capacitance is c = dQ(V)/dV. The capacitance to be used in the formula for the resonant frequency is the incremental capacitance, where it is assumed that the voltage excursions dV are small compared to V. Finite voltages give rise to nonlinearities. Efforts may be made to reduce these nonlinearities in some cases.
The capacitance decreases as the reverse bias increases, according to the relation C = Co/(1 + V/Vo)n, where Co and Vo are constants. Vo is approximately the forward voltage of the diode. The exponent n depends on how the doping density of the semiconductors depend on distance away from the junction. For a graded junction (linear variation), n = 0.33. For an abrupt junction (constant doping density), n = 0.5. If the density jumps abruptly at the junction, then decreases (called hyperabrupt), n can be made as high as n = 2. I expect that the doping on one side of the junction is heavy, and the depletion layer is predominately on one side, but this is a constructional detail.
------------------------------------------------------------------------------------------------
Varactor Theory
A varactor is also known as a variable capacitance diode or a varicap. It provides an electrically controllable capacitance, which can be used in tuned circuits. It is small and inexpensive, which makes its use advantageous in many applications. Its disadvantages compared to a manually controlled variable capacitor are a lower Q, nonlinearity, lower voltage rating and a more limited range. Background material on varactors can be found in the Reference.
Any PN junction has a junction capacitance that is a function of the voltage across the junction, as discussed in any account of PN junctions. The electric field in the depletion layer that is set up by the ionized donors and acceptors is responsible for the voltage difference that balances the applied voltage. A higher reverse bias widens the depletion layer, uncovering more fixed charge and raising the junction potential. The capacitance of the junction is C = Q(V)/V, and the incremental capacitance is c = dQ(V)/dV. The capacitance to be used in the formula for the resonant frequency is the incremental capacitance, where it is assumed that the voltage excursions dV are small compared to V. Finite voltages give rise to nonlinearities. Efforts may be made to reduce these nonlinearities in some cases.
The capacitance decreases as the reverse bias increases, according to the relation C = Co/(1 + V/Vo)n, where Co and Vo are constants. Vo is approximately the forward voltage of the diode. The exponent n depends on how the doping density of the semiconductors depend on distance away from the junction. For a graded junction (linear variation), n = 0.33. For an abrupt junction (constant doping density), n = 0.5. If the density jumps abruptly at the junction, then decreases (called hyperabrupt), n can be made as high as n = 2. I expect that the doping on one side of the junction is heavy, and the depletion layer is predominately on one side, but this is a constructional detail.
---------------------------------------------------------------------------------------
Varactor Theory
A varactor is also known as a variable capacitance diode or a varicap. It provides an electrically controllable capacitance, which can be used in tuned circuits. It is small and inexpensive, which makes its use advantageous in many applications. Its disadvantages compared to a manually controlled variable capacitor are a lower Q, nonlinearity, lower voltage rating and a more limited range. Background material on varactors can be found in the Reference.
Any PN junction has a junction capacitance that is a function of the voltage across the junction, as discussed in any account of PN junctions. The electric field in the depletion layer that is set up by the ionized donors and acceptors is responsible for the voltage difference that balances the applied voltage. A higher reverse bias widens the depletion layer, uncovering more fixed charge and raising the junction potential. The capacitance of the junction is C = Q(V)/V, and the incremental capacitance is c = dQ(V)/dV. The capacitance to be used in the formula for the resonant frequency is the incremental capacitance, where it is assumed that the voltage excursions dV are small compared to V. Finite voltages give rise to nonlinearities. Efforts may be made to reduce these nonlinearities in some cases.
The capacitance decreases as the reverse bias increases, according to the relation C = Co/(1 + V/Vo)n, where Co and Vo are constants. Vo is approximately the forward voltage of the diode. The exponent n depends on how the doping density of the semiconductors depend on distance away from the junction. For a graded junction (linear variation), n = 0.33. For an abrupt junction (constant doping density), n = 0.5. If the density jumps abruptly at the junction, then decreases (called hyperabrupt), n can be made as high as n = 2. I expect that the doping on one side of the junction is heavy, and the depletion layer is predominately on one side, but this is a constructional detail.
---------------------------------------------------------------------------------------------------------------------------------------------
Varactor Devices
The VARACTOR is another of the active two-terminal diodes that operates in the microwave range. Since the basic theory of varactor operation was presented in NEETS, Module 7, Introduction to Solid-State Devices and Power Supplies, Chapter 3, only a brief review of the basic principles is presented here.
The varactor is a semiconductor diode with the properties of a voltage-dependent capacitor. Specifically, it is a variable-capacitance, pn-junction diode that makes good use of the voltage dependency of the depletion-area capacitance of the diode.
In figure 2-42, view (A), two materials are brought together to form a pn-junction diode. The different energy levels in the two materials cause a diffusion of the holes and electrons through both materials which tends to balance their energy levels. When this diffusion process stops, the diode is left with a small area on either side of the junction, called the depletion area, which contains no free electrons or holes. The movement of electrons through the materials creates an electric field across the depletion area that is described as a barrier potential and has the electrical characteristics of a charged capacitor.
-------------------------------------------------------------------------------
Varactor Devices
The VARACTOR is another of the active two-terminal diodes that operates in the microwave range. Since the basic theory of varactor operation was presented in NEETS, Module 7, Introduction to Solid-State Devices and Power Supplies, Chapter 3, only a brief review of the basic principles is presented here.
The varactor is a semiconductor diode with the properties of a voltage-dependent capacitor. Specifically, it is a variable-capacitance, pn-junction diode that makes good use of the voltage dependency of the depletion-area capacitance of the diode.
In figure 2-42, view (A), two materials are brought together to form a pn-junction diode. The different energy levels in the two materials cause a diffusion of the holes and electrons through both materials which tends to balance their energy levels. When this diffusion process stops, the diode is left with a small area on either side of the junction, called the depletion area, which contains no free electrons or holes. The movement of electrons through the materials creates an electric field across the depletion area that is described as a barrier potential and has the electrical characteristics of a charged capacitor.
---------------------------------------------------------------------------------------------------
Varactor Devices
The VARACTOR is another of the active two-terminal diodes that operates in the microwave range. Since the basic theory of varactor operation was presented in NEETS, Module 7, Introduction to Solid-State Devices and Power Supplies, Chapter 3, only a brief review of the basic principles is presented here.
The varactor is a semiconductor diode with the properties of a voltage-dependent capacitor. Specifically, it is a variable-capacitance, pn-junction diode that makes good use of the voltage dependency of the depletion-area capacitance of the diode.
In figure 2-42, view (A), two materials are brought together to form a pn-junction diode. The different energy levels in the two materials cause a diffusion of the holes and electrons through both materials which tends to balance their energy levels. When this diffusion process stops, the diode is left with a small area on either side of the junction, called the depletion area, which contains no free electrons or holes. The movement of electrons through the materials creates an electric field across the depletion area that is described as a barrier potential and has the electrical characteristics of a charged capacitor.
 |
No hay comentarios:
Publicar un comentario