Memory aid: if something 'drops' it is 'lower'

The forward voltage drop of a diode is determined by the material used to manufacture the device. The voltage drop occurs as current flows across the material that makes up the PN junction. Germanium typically has a 0.25-0.3 Volt change. Silicon typically has a 0.7 Volt change. Light Emitting Diodes (LEDs) typically have a 1.4 Volt change. 1

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A Diode is an electronic component that only allows current to flow one direction across it; the most commonly known type of diode these days is an LED (Light Emitting Diode). There are many flashlights and even house lights that are made of LEDs and they are indeed diodes which only allow current to flow in one direction (and then also happen to emit light when that happens).

A resistor allows current to flow both directions but resists the flow of current. A Fuse is something that generally allows current to flow in either direction but when too much current (or at too high of a voltage) flows across it the fuse "blows" (is destroyed) and the flow of current stops. A driven element is the part of an antenna that a transmitter causes to emit RF energy.

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Tags: electronics electrical components arrl chapter 3 arrl module 5

A transistor has three terminals; on the most common type of transistor (a bipolar transistor) these are Base, Collector, and Emitter. Current applied to the Base controls current flow between the collector and emitter, which allows it to work as an electronic switch. The amplifier capabilities are a little more complicated and have to do with the fact that the amount of current directed into the Base is directly proportional to the amount of current that can flow through the Collector and Emitter.

Conversely, a Varistor, also known as a voltage-dependent resistor, is a surge-protecting resistor that varies its resistance based on the applied voltage. A Potentiometer is a variable resistor, and a Thermister is a resistor whose resistance is dependent on temperature. None of these can be used as an electronic switch in any meaningful way.

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Tags: transistors electronics electrical components arrl chapter 3 arrl module 5

While the specifics of how a bipolar junction transistor works is beyond the scope of this explanation, it may be helpful to remember that nearly any time you hear the term "semiconductor" in casual electronic jargon someone is talking about either a transistor specifically or about something made with many transistors (such as an integrated circuit).

This can be remembered by two types of transistor “NPN” or “PNP” where each letter refers to one of the three layers that make them up.

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The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs are devices with three terminals: source, gate, and drain. FETs control the flow of current by the application of a voltage to the gate, which in turn alters the conductivity between the drain and source.

Memory aid: Fields (field-effect transistors) have gates (gate, drain, source are the parts of an FET)

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Electrical components can be small. Sometimes too small to be able to read letters or words. Might also think of a "striped cat"

Click for a list of schematic symbols.

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Diodes only allow current to flow in one direction -- Light Emitting Diodes are still diodes, so the light comes from the forward current which is allowed to go across the LED.

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A Field Effect Transistor controls voltage and current like a regular transistor, but can operate on a much smaller signal, which makes it ideal for radio receivers. It operates using an electric field to control the shape of the channel in the semi-conductor material.

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Electrodes are refered to as either Anodes or Cathodes regardless of whether they are on a diode or other component. Current flows into an Anode and out of a Cathode.

Plus and Minus indicate a positive or negative voltage on a power source but are not strictly speaking names for electrodes. Source, Gate and Drain are terminals on a Field Effect Transistor (FET). Base, Collector and Emitter are terminals on a bipolar transistor.

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Transistor is the only component in this list that has gain.

A transformer may have a high secondary voltage ratio and be used for increasing voltage, or it may have a high secondary current ratio and be used for increasing current, but these increases and decreases are called transformation or conversion not gain.

So the only option that makes sense in this list is Transistor.

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Gain is defined as being the ratio of the output power to the input power, or in other words it refers to how much power is gained when passing through the transistor. Just remember that "you gain a lot through amplification".

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Bipolar Transistor - A semiconductor device having three electrodes: emitter, base, and collector. It is effectively a sandwich of two types of doped semiconductor, usually p-type and n-type silicon, and so contains two p-n junctions.

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