Guide to Transistors--Article Index

Contents:

1. The World of the Atom

Elements. Compounds and mixtures. Union of elements. Atoms. Mass of the atom. The magnetic field of the electron. Orbital electrons. Shells. Multiple orbits. Shared electrons. Atomic structure. Atoms and molecules. Electrons in motion. Conductors. Insulators. Semiconductors. Germanium. Valence electrons. Valence bond. Electron behavior. Doping or adding impurities. Lattice structure. The donors--antimony, arsenic, phosphorus and bismuth. The acceptors - boron, aluminum, gallium, indium and thallium. Diffusion. Holes. P-type and n-type germanium. Current flow. Gallium arsenide and the tunnel diode.

2. The Diode

N-type and p-type germanium. Recombination and movement. Net charge of atoms. Donors and acceptors join to make a diode. The p-n junction. Movement of charges. The electric field barrier. Lines of force. Ionization. The measurable junction voltage. The p-n barrier. Interface potential. Bias and the potential barrier. Positive and negative ions. Ionization and de-ionization. Hole and electron movement. Forward and reverse bias. Forward or reverse current. The diode. Graphs. Avalanche multiplication and breakdown. Zener diode. Controlling resistance.

3. Enter the Triode

P-n and n-p diodes. Emitter, base and collector. The transistor. Biasing the transistor. Addition of signal and bias voltages. Resistance, reactance and impedance. Values of signal and bias volt ages. Impedance reference. Collector bias. Input and output circuits. The transistor symbols. Formation of p-n-p and n-p-n transistors. P-n-p and n-p-n circuitry. Adding components. How the transistor works. Electron flow in the n-p-n transistor. Amplification. Current amplification--alpha. Current amplification--beta. Collector current vs emitter current. Transistor as an oscillator. Feedback.

4. Transistor Characteristics

Biasing methods and requirements. Biasing with one or two batteries. Fixed bias. Making the bias self-adjusting. Self bias. Bias voltage divider. Collector voltage vs collector current. Static testing. Collector characteristic curve. Tube vs transistor biasing. Collector characteristic family. Collector load. How to determine the load line. Other values of load. Distortion. Transfer characteristic curves. Mutual or transfer characteristics. Stabilization. Effects of temperature. Current feedback. Voltage feedback. Input resistance. Measuring input resistance. Output resistance.

5. Audio Amplifiers

Basic transistor amplifier circuit. Amplifier arrangements. The common-emitter circuit. Complementary symmetry. Biasing the amplifier. Classes of amplifiers. Base bias line. Class A vs Class B. Voltage and power amplifiers. Class A, single-ended, power amplifier. Capacitor polarity. Resistance and transformer coupling. Stability of operation. Temperature coefficients. Thermistors. Preventing thermal runaway. Heat sink. Efficiency--Class A. The pushpull amplifier. Efficiency--Class B and AB. Power output. Adjusting the bias. Driver stage. Emitter follower (grounded collector). Direct-coupled drive. Diode compensation.

6. Detectors, AGC, IF Amplifiers and Front Ends

Transistor detectors. Unbiased base operation. Detection and amplification. Decoupling. 2-transistor receivers. Automatic gain control. Diode detection and age. Development of age. Decoupling. Auxiliary age. Shunted diode age. Weak and strong signals. Impedance matching. Tapped collector winding. Base and collector matching. Negative feedback and neutralization. Basic neutralizing circuits. Feed back variations. Problem of selectivity. Ferrite antennas. Frequency conversion. Converters. Autodyne converter. Local oscillator. Operating frequency. Transformers and autotransformers. Mixer and rf amplifier.

7. Transistor Types

Transit time. Capacitance of a diode. Alpha cutoff frequency. Tetrode transistor. Surface-barrier transistor. Diffused transistor. Micro alloy transistor. Junction transistors. Intrinsic transistors. Hook transistors. Field-effect transistor. Gate electrode. Source and the drain. Point-contact transistor. Multi-headed transistors. Tandem transistors. Germanium and silicon. Evaporation-fused transistors. Transistor dimensions. Manufacturing transistors. Crystalline formation. Power transistors. Alloy-junction transistors. Number of leads. Techniques of mounting transistors. Circuit packaging. Other transistor types. Inverters, flip-flops, choppers and amplifiers.

8. Circuit Analysis

The basic circuit, Meter amplifier. Increasing meter sensitivity. Transistor relay amplifier. Preamplifier circuit. Using a solar cell. Methods of connecting electrolytic capacitors. Signal tracer. Re arranging the circuit. Transformer-coupled audio amplifier. A transistor receiver with minimum parts. Transistors as a voltage divider. Common-collector amplifier. Advantage of redrawing the circuit. Oscillators. The multivibrator. Crystal-controlled transistor oscillators. The transistor as a switch.

Introduction

COLUMBUS is popularly known as a hardy and venturesome explorer who tested his beliefs in a very practical manner, but long before Christopher, other lesser known adventurers probed the American coastline. And, in the same way, while John Bardeen and Walter H. Brattain of Bell Telephone Laboratories are deservedly credited with the invention of the transistor, many others, some long before these two, poked, probed, tested the very curious and intriguing properties of crystalline materials.

As far back as 1855, and that is really reaching into the far recesses of the beginnings of electronics, some of the basic proper ties of semiconductors had been investigated. Even before then in 1835, an enterprising researcher by the name of Munk Af Rosenschold had been doing experiments on electrical conduction in solids. And still earlier, in 1833, Michael Faraday was learning about temperature coefficients of solids.

These tidbits of knowledge kept adding to a growing mass of information about solids, yet they remained unrelated, waiting for the beginnings of electronics communications. Although wireless communication did start to stir during the latter portion of the 19th century, it wasn't until the end of World War I that the direct ancestor of the transistor made its appearance as the cat's whisker crystal. This was a true semiconductor but its function was solely that of a rectifier. It is amusing to wonder whether, if the triode vacuum tube had not appeared to replace the crystal detector, some enterprising soul might not have found practical ways of making crystals amplify and oscillate. A few loyal investigators were sufficiently impressed with semiconductors to continue their work. Gabel V. Lossev in 1924 described the possibilities of the crystal as a generator and amplifier. And, in 1928, R. S. Ohl obtained a patent for a multi-electrode crystal that would amplify and oscillate. He was also the discoverer, in 1941, of the p-n junction, basically the heart of the modern transistor.

But we must assign the formal birth date of the transistor to June 1948, when Bell Telephone Laboratories first announced it.

This transistor, a type not now used, was called the point contact and basically was a germanium diode, but with two cat's-whiskers instead of the one associated with the old-time crystal detector.

Containing three leads, known as the emitter, collector and base, the device could be used to amplify and oscillate.

Of course this was just the beginning but, if the transistor was somewhat slow in getting started (compared to vacuum tubes), this tiny device has made gigantic strides. And, that brings us to the purpose of this guide ... to explain what the transistor is, how it works and just how it behaves in the presence of such well known companions as resistors, coils and batteries. The treatment here is nonmathematical, with many of the explanations by analogy-a dangerous procedure if rigorous exactness is demanded. This book will, however, give you a good general understanding of transistors, and, if that whets your appetite for a more definitive knowledge, so much the better.