10-30-2014 diodes and transistors

When the negative end of the circuit is hooked up to the N-type layer and the positive end is hooked up to P-type layer, electrons and holes start moving and the depletion zone disappears.

When the positive end of the circuit is hooked up to the N-type layer and the negative end is hooked up to the P-type layer, free electrons collect on one end of the diode and holes collect on the other. The depletion zone gets bigger.

A transistor is a semiconductor, meaning that sometimes it conducts electricity, and sometimes it doesn’t. Its internal resistance varies, depending on the power that you apply to its base. NPN and PNP transistors are bipolar semiconductors. They contain two slightly different variants of silicon, and conduct using both polarities of carriers—holes and electrons

The amplifier you just built was an analog amplifier.  The term “analog amplifier” refers to a circuit that can take an input voltage that can vary continuously over time and either boost the voltage or current to create a higher power output signal that also varies continuously over time.  Many ICs are digital rather than analog circuits.  Let’s explore the meaning of the term “digital.”

            Counting and displaying numerals, as in a digital watch, are operations that require a different type of electronic signal and circuitry than the continuously varying signal characteristic of audio electronics.  Digital electronics involves voltages that are either “on” or “off.”  The voltage is either zero (“off”) or at some other fixed voltage which is defined as “on.”  The 0 and 15 Volt digital circuitry you will be using will interpret any voltage greater than about 3 V as an “on” state and any voltage less than about 2 V as an “off” state.  One advantage of digital circuitry is that it is remarkably insensitive to stray variations or “noise.”  Thus, digital recorders, computers, and other modern digital devices are vastly more accurate and reliable than circuitry that attempts to reproduce varying signals.

When the base emitter junction is forward biased, a small current will flow into the base. Therefore holes are injected into the P type material. These holes attract electrons across the forward biased base/emitter junction to combine with the holes. However, because the emitter region is very heavily doped, many more electrons cross into the base region than are able to combine with holes. This means there is a large concentration of electrons in the base region and most of these electrons are swept straight through the very thin base, and into the base/collector depletion layer. Once here, they come under the influence of the strong electric field across the base/collector junction. This field is so strong due to the potential gradient in the collector material mentioned earlier, that the electrons are swept across the depletion layer and into the collector material, and so towards the collector terminal

This is a clean bread board. It has a bright future and infinite possibilities. Every hole is a new possible circuit that could lead to the next big thing. THE NEXT BIG THING.