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www.play-hookey.com | Thu, 03-04-2021 |
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Direct Current
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Semiconductors
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| Basic Semiconductor Structures | Field Effect Transistors (FETs) | Adding More Junctions | Specialized Devices | | ||
| The Four-Layer Diode | The Silicon Controlled Rectifier | The Silicon Controlled Switch | The Diac and Triac | |
Semiconductors: Adding More Junctions |
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The transistors we studied earlier have no more than two junctions, to form NPN or PNP bipolar transistors. What happens if we build devices with more junctions? What might a PNPN device be able to do? How about a 5-layer device, either PNPNP or NPNPN? Could we make any practical use of such a device?
Let's start by adding one layer to a bipolar junction transistor. This gives us a PNPN structure.
Now let's add a connection to the internal P-type layer.
Next, we add a connection to the internal N-type layer, to gain access to all regions of the device.
Now it's time to get fancy. Can we arrange it so the device can conduct current in either direction, and still be controlled?
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