Diode and transistor Flashcards
(29 cards)
What is a diode?
A diode is a semiconductor with two terminals, the anode and the cathode, that typically allows current to flow in one direction only.
What are the two types of resistance a diode has?
- Low resistance in one direction
- High resistance in the other direction
What is a key application of diodes?
To steer current to flow in the required direction.
What does a battery convert?
A battery converts chemical energy into electrical energy in the form of DC voltage.
What is a major drawback of batteries?
They require charging.
What must AC current be converted to before charging a battery?
DC current.
What are rectifiers?
Rectifiers are circuits made up of either one diode (half wave rectification) or four diodes (full wave rectification).
What is the process called that chemically changes silicon to control its electrical properties?
Doping.
What are the two types of impurities added in silicon doping?
- N-type: extra electrons creating a negative charge
- P-type: absence of an electron creating a positive ‘hole’
What happens when N-type and P-type silicon junctions are connected?
A diode is created that allows current to flow in one direction only.
What is the forward bias in a diode?
When the positive of a battery is connected to the P-side (anode) and the negative to the N-side (cathode).
What is the reverse bias in a diode?
When the positive is connected to the N-side and the negative to the P-side, preventing current flow.
What is the typical voltage required for current to flow through a diode?
About 0.7V.
What is Peak Inverse Voltage (PIV)?
The maximum reverse voltage a diode can withstand without conducting.
What does half wave rectification do?
Allows current to flow only during one half of the AC cycle.
What does full wave rectification do?
Allows current to flow during both halves of the AC cycle.
What is a transistor?
A transistor is a three-connection P-N junction device used to regulate or control voltage and current flow.
What are the two common designs of transistors?
- NPN
- PNP
What are the three connections of a transistor called?
- Base
- Collector
- Emitter
How does a transistor amplify current?
By applying a small voltage on the base, allowing a larger current to flow between the collector and emitter.
What happens when the base supply of a transistor is removed?
The transistor switches off.
What is the current gain of an amplifier?
The current flowing between collector and emitter is larger than the base current.
What is a key advantage of transistors as switches?
They can switch very quickly (over 100 million on/off cycles a second) and have no mechanical parts.
In what applications are transistors used to regulate current?
In marine applications for propulsion drives on big cruise ships.
