L16+L17+L18: Transistors Flashcards
What is a Bipolar Junction Transistor (BJT)
- A bipolar junction transistor is a semiconductor device used to amplify tor switch electrical signals and electrical power
- A transistor is made of semiconductor material (e.g Si, Ge)
What can the function of a Transistor be compared to
What does a Bipolar Junction Transistor (BJT) consist of
What does the term Bipolar in a BJT reflect?
The term bipolar reflects the fact that Holes & Electrons participate in the injection process into the oppositely polarised material.
If only one carrier is employed, it is considered a unipolar device.
What are the different terminals of a Bipolar Junction Transistor
How does conventional current flow in a npn transistor compared to a pnp transistor
What are the majority current carriers in a npn transistor
What are the majority current carriers in a pnp transistor
In pnp transistors, the majority current carriers are:
- Holes in the emitter and collector
- Free eletrons in the base
What is the Structure of a Bipolar Junction Transistor (BJT)
The operation of the transistor is very dependant on the degree of doping of its various parts.
- The emitter region is heavily doped; its job is to emit carriers into the base
- The base region is very thin and lightly doped. Most of the current carriers injected into the base, pass on to the collector
- The collector region is moderately doped and is the largest of all three regions; its function is to collect or attract current carriers from the base region.
Do the Collector, Base, and Emitter have high or low density of free electrons/holes
What is the Operating Principle for a Bipolar Junction Transistor (What happens at each point/stage as the free electrons pass through)
What is the Emitter Current from a Transistor
How are Transistors Biased in this Circuit
What is the DC current gain of a transistor referred to as (and what are the equations for βdc)
What is DC Alpha
What is the DC Beta of a transistor
How is DC Beta usually designated on data sheets
DC Beta is usually designated on the data sheets as an equivalent hybrid parameter (hFE)
Equation for DC Beta
How can DC Alpha and be related to DC Beta
What needs to be varied to allow a transistor to operate in what 4 regions
By varying IB (base current), a transistor can be made to operate in one of the 4 regions:
* Active Region
* Saturation Region
* Cutoff Region
* Breakdown Region
These regions are defined based on the collector current, Ic vs. collector-emitter voltage characteristic, VCE
What is the Saturation Region
What is the Cutoff Region
What is the Active Region
What is the Ic against VCE that shows all four transistor regions
What do transistors in the Saturation, Cutoff, and Active Regions act like
- Saturation corresponds to a closed switch
- Cut-off corresponds to an open switch
- In the active region, the collector circuit acts like a current source.
How is the amount of base current (IB) and collector current (IC) controlled an emitter connect
What happens in the breakdown region of a transistor
What things in a transistor are limited with Maximum Ratings
How can a transistor be modelled (in terms of input and output)
How can the DC equivalent circuit of a transistor be shown
What are the three most commonly used biasing techniques for transistors
- Base Bias
- Voltage-Divider
- Emitter Bias
What does a Base Bias circuit look like
What does a Voltage-Divider circuit for transistor biasing look like
What does an Emitter Bias circuit look like
How does the Base Bias Technique Work
What is the Q point of a transistor circuit
What is Q considered to be in the Active Region
Where is a Q point set in a properly biased amplifier
A properly biased amplifier has a Q point that is set at or near the centre of the active region,
