Electronics

Cunife Telephone Transmission Line

For decades prior to 1984, the Bell System provided both local and long distance service throughout most of the United States. In the 1970s, the U.S. Federal Government came to believe that this was an illegal monopoly and sued to break it up. The government won, and on January 1, 1984, AT&T was broken up [...]

{ 0 comments }

Wide Area Networks

A wide area network, or WAN, spans a large geographical area, often a country or continent. It contains a collection of machines intended for running user (i.e., application) programs. We will follow traditional usage and call these machines hosts. The hosts are connected by a communication subnet, or just subnet for short. The hosts are [...]

{ 0 comments }

Hardwares of Networking

It is now time to turn our attention from the applications and social aspects of networking (the fun stuff) to the technical issues involved in network design (the work stuff). There is no generally accepted taxonomy into which all computer networks fit, but two dimensions stand out as important: transmission technology and scale. We will [...]

{ 0 comments }

Light Activated SCR

Like bipolar transistors, SCRs and TRIACs are also manufactured as light-sensitive devices, the action of impinging light replacing the function of triggering voltage. Optically-controlled SCRs are often known by the acronym LASCR, or Light Activated SCR. Its symbol, not surprisingly, looks like this: Optically-controlled TRIACs don’t receive the honor of having their own acronym, but [...]

{ 1 comment }

TRIAC

SCRs are unidirectional (one-way) current devices, making them useful for controlling DC only. If two SCRs are joined in back-to-back parallel fashion just like two Shockley diodes were joined together to form a DIAC, we have a new device known as the TRIAC: Because individual SCRs are more flexible to use in advanced control systems, [...]

{ 0 comments }

Shockley Diode

Our exploration of thyristors begins with a device called the four layer diode, also known as a PNPN diode, or a Shockley diode after its inventor, William Shockley. This is not to be confused with a Schottky diode, that two-layer metal-semiconductor device known for its high switching speed. A crude illustration of the Shockley diode, [...]

{ 0 comments }

Common Base Amplifier

Common Base Amplifier: The final transistor amplifier configuration we need to study is the common-base. This configuration is more complex than the other two, and is less common due to its strange operating characteristics. It is called the common base configuration because (DC power source aside), the signal source and the load share the base [...]

{ 0 comments }

Common Emitter Amplifier Operation

At the beginning of this chapter we saw how transistors could be used as switches, operating in either their “saturation” or “cutoff” modes. In the last section we saw how transistors behave within their “active” modes, between the far limits of saturation and cutoff. Because transistors are able to control current in an analog (infinitely [...]

{ 0 comments }

The Transistor as a Switch

A transistor collector current is proportionally limited by its base current, it can be used as a sort of current controlled switch. A relatively small flow of electrons sent through the base of the transistor has the ability to exert control over a much larger flow of electrons through the collector. Suppose we had a [...]

{ 0 comments }

← Previous Entries