69 lines
1.9 KiB
Markdown
69 lines
1.9 KiB
Markdown
There are two types of transistors:
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# Bipolar Junctions Transistors (BJT)
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![[bipolar-junction-transistor|200x]]
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The current flowing in from Base controls the much larger current flowing between Collector and Emitter.
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## Rules for NPN Transistors
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**1. Polarity**
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The collector must be more positive than the emitter.
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**2. Junctions**
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The base$\rightarrow$emitter and base$\rightarrow$collector connections behave like diodes.
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**3. Maximum Ratings**
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Any transistor has maximum ratings for $I_C$ ,$I_B$ and $V_{CE}$ that should not be exceded.
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**4. Current Amplifier**
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When rules 1-3 are obeyed, $I_C$ is roughly equivalent to $IB$ and can be written like:
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$\displaystyle I_C = \beta I_B$
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In the following example circuit we can see that for a $\beta$ of 100 the Ic current is aroung 100 times higher than the base current.
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```circuitjs
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$ 1 0.000005 11.086722712598126 50 5 43 5e-11
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R 256 16 256 -48 0 0 40 2 0 0 0.5
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g 256 144 256 208 0 0
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t 192 80 256 80 0 1 -1.552 0.44799999999999995 100 default
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R 144 80 64 80 0 0 40 0.44799999999999995 0 0 0.5
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w 256 16 256 64 3
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w 256 96 256 144 3
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w 144 80 192 80 1
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x 272 -5 289 -2 4 24 C
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x 273 179 289 182 4 24 E
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x 96 68 112 71 4 24 B
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x 266 82 275 85 4 12 Ic
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o 1 16 0 159745 0.0001 0.0001 0 2 1 3
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38 3 F1 0 0 1.4 -1 Voltage
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```
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## NPN vs PNP Transistors
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The names come from the way they are constructed
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![[bjt-transistors.png]]
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![[transistors-pnp-npn]]
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# Transistor Modes
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## Saturation
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In this mode the transistor acts like a short circuit and current flows freely from emitter to collector.
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## Cut-Off
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In this mode the transistor acts like an open circuit and no current flows from emitter to collector.
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When $V_C > V _B < V_E$ then the transistor acts in Cutoff Region
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## Active
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The current from collector to emitter is proportional to the current flowing into the base.
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# Field-Effect Transistors (FET)
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![[field-effect-transistor|200x]]
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