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Chapter – 2

Chapter – 2. Logic Families. Classification of Logic Families. Bipolar logic families. Bipolar logic families. Unipolar logic families. Characteristics of Digital ICs. Fan out Fan in Propagation delay Power dissipation Noise margin / noise immunity Figure of merit

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Chapter – 2

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  1. Chapter – 2 Logic Families

  2. Classification of Logic Families

  3. Bipolar logic families

  4. Bipolar logic families

  5. Unipolar logic families

  6. Characteristics of Digital ICs • Fan out • Fan in • Propagation delay • Power dissipation • Noise margin / noise immunity • Figure of merit • Current and voltage • Power supply requiems • Operating temperature range • Flexibility available.

  7. Characteristics of Digital ICs

  8. Characteristics of Digital ICs • Fan out- is defined as the maximum no. of logic gates which can be driven by a gate • Higher the fan out higher the current supplying capacity of a gate. • Fan in – the no of inputs gate. • for example a two i/p gate will have fan in equal to 2.

  9. Propagation delay • The delay time are measured between 50% voltage level of i/p & o/p waveform. • There are two delay time- tPHL & tPLH • tPHL – when o/p goes from high state to low state. • tPLH- when o/p goes from low state to high state.

  10. Power dissipation

  11. Power dissipation

  12. Noise margin / noise immunity • Noise margin -Noise is an unwanted electrical disturbance which may induce some voltage in the connecting wires used between two gates. • Noise immunity -The circuit ability to tolerate noise signal is referred as the noise immunity.

  13. Figure of merit

  14. Current and voltage para. • VIH = High level input voltage. • VIL = Low level input voltage. • VOL= Low level output voltage. • VOH= High level output voltage. • IIL = Low level input current. • IIH = High level input current.

  15. Power supply requiems- • The amount of power required by IC is important to choose proper power supply. • Operating temperature range- • Industrial application is 0oC to 70oC • Military application is -55oC to 125oC

  16. Important logic families are • TTL- • It is a transistor transistor logic. • This is most popular logic family as lot of functions are available in the family • The important series are 74xx & 54xx • It works with power supply of +5v.

  17. The multiple emitter transistor

  18. Two input TTL-NAND Gate

  19. Two input TTL-NAND Gate

  20. Totem-pole arrangement • The arrangement of Q3 & Q4 on the o/p side of a TTL NAND gate is called as the totem -pole arrangement

  21. Advantages • Low propagation delay • High power dissipation • High current sourcing and sinking capabilties.

  22. TTL Characteristics

  23. Positive logic- logic 0 = 0v logic1 = +5v • Negative logic - logic 0 = +5v logic1 = 0v

  24. Open collector 2 i/p NAND gate

  25. Open collector 2 i/p NAND gate

  26. Open collector 2 i/p NAND gate

  27. Comparison

  28. Emitter coupled logic

  29. Emitter coupled logic

  30. Emitter coupled logic

  31. Emitter coupled logic

  32. Emitter coupled logic- NOT gate

  33. Emitter coupled logic

  34. ECL Characteristics

  35. Emitter coupled logic

  36. MOS LOGIC FAMILIES

  37. MOS LOGIC FAMILIES

  38. N-MOS CIRCUIT

  39. N-MOS INVERTER

  40. N-MOS INVERTER

  41. N-MOS INVERTER

  42. N-MOS NAND GATE

  43. N-MOS NAND GATE

  44. N-MOS NOR GATE

  45. N-MOS NOR GATE

  46. P-MOS INVERTER GATE

  47. P-MOS INVERTER GATE

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