Author: admin
-
2.2 Quantum Physics
“I think it is safe to say that no one understands quantum mechanics.” —Physicist Richard P. Feynman To say that the invention of semiconductor devices was a revolution would not be an exaggeration. Not only was this an impressive technological accomplishment, but it paved the way for developments that would indelibly alter modern society. Semiconductor…
-
2.1 Introduction to Solid-state Device Theory
This chapter will cover the physics behind the operation of semiconductor devices and show how these principles are applied in several different types of semiconductor devices. Subsequent chapters will deal primarily with the practical aspects of these devices in circuits and omit theory as much as possible. Back to Main Index of Book
-
1.7 Attenuators
What is Attenuators? Attenuators are passive devices. It is convenient to discuss them along with decibels. Attenuators weaken or attenuate the high level output of a signal generator, for example, to provide a lower level signal for something like the antenna input of a sensitive radio receiver. (figure below) The attenuator could be built into…
-
1.6 Absolute dB scales
Decibel as Absolute Unit of Power It is also possible to use the decibel as a unit of absolute power, in addition to using it as an expression of power gain or loss. A common example of this is the use of decibels as a measurement of sound pressure intensity. In cases like these, the…
-
1.5 Decibels
The Bel is Used to Represent Gain In its simplest form, an amplifier’s gain is a ratio of output over input. Like all ratios, this form of gain is unitless. However, there is an actual unit intended to represent gain, and it is called the bel. As a unit, the bel was actually devised as…
-
1.4 Amplifier Gain
The Voltage Gain Because amplifiers have the ability to increase the magnitude of an input signal, it is useful to be able to rate an amplifier’s amplifying ability in terms of an output/input ratio. The technical term for an amplifier’s output/input magnitude ratio is gain. As a ratio of equal units (power out / power…
-
1.3 Amplifiers
Practical Benefit of Active Devices The practical benefit of active devices is their amplifying ability. Whether the device in question be voltage-controlled or current-controlled, the amount of power required of the controlling signal is typically far less than the amount of power available in the controlled current. In other words, an active device doesn’t just…
-
1.2 Active Versus Passive Devices
Passive Devices Components incapable of controlling current by means of another electrical signal are called passive devices. Resistors, capacitors, inductors, transformers, and even diodes are all considered passive devices. Active Devices An active device is any type of circuit component with the ability to electrically control electric charge flow (electricity controlling electricity). In order for…
-
1.1 From Electric to Electronic
Introduction This third volume of the book series Lessons In Electric Circuits makes a departure from the former two in that the transition between electric circuits and electronic circuits is formally crossed. Electric circuits are connections of conductive wires and other devices whereby the uniform flow of electric charges occurs. Electronic circuits add a new…
-
14.8 Waveguides
A waveguide is a special form of transmission line consisting of a hollow, metal tube. The tube wall provides distributed inductance, while the empty space between the tube walls provide distributed capacitance. Wave guides conduct microwave energy at lower loss than coaxial cables. Waveguides are practical only for signals of extremely high frequency, where the…
-
14.7 Impedance Transformation
Standing waves at the resonant frequency points of an open- or short-circuited transmission line produce unusual effects. When the signal frequency is such that exactly 1/2 wave or some multiple thereof matches the line’s length, the source “sees” the load impedance as it is. The following pair of illustrations shows an open-circuited line operating at…
-
14.6 Standing Waves and Resonance
Whenever there is a mismatch of impedance between transmission line and load, reflections will occur. If the incident signal is a continuous AC waveform, these reflections will mix with more of the oncoming incident waveform to produce stationary waveforms called standing waves. The following illustration shows how a triangle-shaped incident waveform turns into a mirror-image reflection upon…
-
Vol II. Credits
All entries arranged in alphabetical order of surname. Major contributions are listed by individual name with some detail on the nature of the contribution(s), date, contact info, etc. Minor contributions (typo corrections, etc.) are listed by name only for reasons of brevity. Please understand that when I classify a contribution as “minor,” it is in…
-
14.5 Long and Short Transmission Lines
In DC and low-frequency AC circuits, the characteristic impedance of parallel wires is usually ignored. This includes the use of coaxial cables in instrument circuits, often employed to protect weak voltage signals from being corrupted by induced “noise” caused by stray electric and magnetic fields. This is due to the relatively short timespans in which…
-
14.4 Finite-length Transmission Lines
A transmission line of infinite length is an interesting abstraction, but physically impossible. All transmission lines have some finite length, and as such do not behave precisely the same as an infinite line. If that piece of 50 Ω “RG-58/U” cable I measured with an ohmmeter years ago had been infinitely long, I actually would…