Digital I/O

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.

18. 74HC04

19. 74HC04

20. Absolute Maximum Ratings Not so Useful Quite Useful

21. Absolute Maximum Ratings

22. Logic Levels and Noise Margins

23. What about Slowly Changing Inputs?

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

26. 74HC14

27. Power Outputs The Darlington

29. DS3658

30. DS3658

32. ULN2003A (1 of 7 per package)

33. ULN2003A Specifications

34. Not all 7 at once !