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Digital I/O

This guide covers the operation of bipolar and MOSFET transistors as switches, including how to turn them on and check their effectiveness. It discusses NPN and PNP bipolar transistors, explaining the importance of forward biasing the base-emitter junction and details about collector-emitter current ratios. The guide also explores MOSFETs, including N-channel and P-channel types, how to activate them via gate-source voltage, and identifying successful operations through voltage drops. Finally, it introduces CMOS technology and highlights critical logic levels, noise margins, and power outputs.

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Digital I/O

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  1. Digital I/O Transistors and Mosfets

  2. Bipolar Transistors used as Switches NPN PNP Collector Emitter Base Base Emitter Collector How do we get them turned on? Forward bias the Base:Emitter Junction Supply current How much current? 1/10th as much as the Collector:Emitter current How do we know if we have been successful? Vce will drop to about 0.2V

  3. Bipolar Transistors used as Switches How do we get them turned on? How do we know if we have been successful?

  4. MOSFET Transistors used as Switches P-Channel N-Channel Drain Drain Gate Gate Source Source How do we get them turned on? |VGS| > Threshold N-Channel: G > S, P-Channel G < S How do we know if we have been successful? RDS will drop to a low value

  5. MOSFET Transistors used as Switches How do we get them turned on? How do we know if we have been successful?

  6. What is CMOS ? Complementary MOS N-Channel and P-Channel used in Pairs

  7. What is CMOS ?

  8. Digital Inputs Logic Levels 0 1 Voltage Levels < Low Threshold > High Threshold

  9. What Are the Voltage Levels? That Depends on the type of logic... Transistor Transistor Logic High-speed CMOS High-speed CMOS, TTL input Original CMOS

  10. How is the Voltage Specified?

  11. It takes Voltage and Current to make a device work

  12. Inter- Connecting

  13. Digital Logic Bipolar TTL Output

  14. Digital Logic Open Collector Output

  15. Digital Logic CMOS Totem Pole

  16. Sizing a pull-up Resistor: Max & Min.

  17. 74HC04

  18. 74HC04

  19. Absolute Maximum Ratings Not so Useful Quite Useful

  20. Absolute Maximum Ratings

  21. Logic Levels and Noise Margins

  22. What about Slowly Changing Inputs?

  23. How do you get Hysterisis ? 1) Schmitt Trigger inputs 2) Comparator with Hysterisis

  24. 74HC14

  25. Power Outputs The Darlington

  26. DS3658

  27. DS3658

  28. ULN2003A (1 of 7 per package)

  29. ULN2003A Specifications

  30. Not all 7 at once !

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