1 / 23

Logic Gates

Logic Gates. Transistors as Switches. EB voltage controls whether the transistor conducts in a common base configuraiton. Logic circuits can be built. AND. In order for current to flow, both switches must be closed Logic notation A B = C. OR. Current flows if either switch is closed

shiloh
Télécharger la présentation

Logic Gates

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Logic Gates

  2. Transistors as Switches • EB voltage controls whether the transistor conducts in a common base configuraiton. • Logic circuits can be built

  3. AND • In order for current to flow, both switches must be closed • Logic notation AB = C

  4. OR • Current flows if either switch is closed • Logic notation A + B = C

  5. Properties of AND and OR • Commutation • A + B = B + A • A  B = B  A Same as Same as

  6. Properties of AND and OR • Associative Property • A + (B + C) = (A + B) + C • A  (B  C) = (A  B)  C =

  7. Properties of AND and OR • Distributive Property • A + B  C = (A + B)  (A + C) • A + B  C

  8. Distributive Property • (A + B)  (A + C)

  9. Binary Addition Notice that the carry results are the same as AND C = A  B

  10. Inversion (NOT) Logic:

  11. Exclusive OR (XOR) Either A or B, but not both This is sometimes called the inequality detector, because the result will be 0 when the inputs are the same and 1 when they are different. The truth table is the same as for S on Binary Addition. S = A  B

  12. Getting the XOR Two ways of getting S = 1

  13. Circuit for XOR Accumulating our results: Binary addition is the result of XOR plus AND

  14. Half Adder Called a half adder because we haven’t allowed for any carry bit on input. In elementary addition of numbers, we always need to allow for a carry from one column to the next. 18 25 3 (plus a carry) 4

  15. Full Adder

  16. Full Adder Circuit

  17. Chaining the Full Adder Possible to use the same scheme for subtraction by noting that A – B = A + (-B)

  18. Binary Counting Use 1 for ON Use 0 for OFF = 00101011 So our example has 25 + 23 + 21 + 20 = 32 + 8 + 2 + 1 = 43 Binary Counter

  19. NAND (NOT AND)

  20. NOR (NOT OR)

  21. Exclusive NOR Equality Detector

  22. Summary

More Related