This document provides an overview of different families of digital integrated circuits, including Resistor-Transistor Logic (RTL), Diode-Transistor Logic (DTL), Transistor-Transistor Logic (TTL), Emitter Coupled Logic (ECL), Metal Oxide Semiconductor (MOS) technologies, and Complementary MOS (CMOS). It discusses the characteristics of each family such as speed, power dissipation, and miniaturization and how newer technologies improved upon older ones, with CMOS now being the most widely used due to its high density, speed and low power capabilities.

1. DIGITAL INTEGRATED
CIRCUITS
• Light introduction to the underlying
technologies
• Some of them historical, some of them
current

2. The Families
• RTL
• DTL
• TTL
• ECL
• N-MOS, P-MOS
• CMOS

3. {R, D, T}TL
• These are
– Resistor Transistor Logic
– Diode Transistor Logic
– Transistor Transistor Logic
• Only TTL survives, although not for long
• Until recently it was the fastest with
reasonable price and power requirements.

4. Bipolar Transistor
• This uses the “classic” bipolar transistor
• In a few cases it was combined with CMOS
for chips marketed as Bi-CMOS

5. ECL
• Emitter Coupled Logic
• The fastest, if money and heat is not an issue
• Used in the supercomputers of the 80s and
90s

6. {N, P}MOS
• Precursors to the CMOS
• Negative or Positive Metal Oxide
Semiconductor
• FET: A fundamentally different kind of
transistor than the one used in TTL
• Stands for Field Effect Transistor

7. CMOS
• THE family: Complementary MOS
• Currently the highest density, speed and
lowest power dissipation.
• Contains both positive and negative channel
transistors

10. Fan-Out
• How many circuits can be driven by the
output of a particular circuit
• It is a property of the driving chip (we
assume that the driven chips are from the
same technology)
• Depends on the technology, clock rate etc

12. Power Dissipation
• The power needed to run the circuit
– each gate needs very little
– there are many gates
• Most of the energy is expended during
switching
• Depends on the technology, clock rate,
voltage etc

13. Miniaturization Helps
• A big factor is stray capacitance
• Smaller circuits have (in general) smaller
capacitance

14. Definition
• The power is
– P = I * V
• I is the average current
• V is the supplied voltage
– A bit more complex than that actually
• We can reduce either.

15. Propagation Delay
• The other big issue
• Used to be number one issue
• Directly affects clock rate

17. Noise Margin
• All circuits have noise
• Some of it is inherent property of electricity
• Some of it is just too expensive to eliminate
• Some of it is just unmodeled issues in the
circuit itself

20. Transistors are Funny
• The base-emitter voltage is about 0.7V when
conducting
• The base-collector voltage is about 0.3V
when saturated
• The collector current is about 50 times the
base current

22. Resistor Transistor Logic
• The gates behave like analog amplifiers
• Low fan out
• Rather slow
• Power hungry
• Kind like a Hummer!

24. Diode Transistor Logic
• Some improvement in fan out
• Fewer resistors more diodes

27. Transistor Transistor Logic
• Small change over DTL
• Several other improvements were applied to
TTL
• Dominated the ICs in the early 80’s

28. Improvements
• The flexibility of the family allows the
manufacturers to offer a variety of grades
• One can trade off speed and power
• A great improvements was the introduction
of the Schottky diode (prevents saturation)

29. Variety of Outputs
• Open collector where user supplies the
output resistor (wired-and)
• Totem pole
• Tristate

30. Nice trick
• Combines the diodes of the DTL into one
multi-emitter transistor

34. Totem Pole
• The output resistor gives us trouble:
– if it has many Ohms, the fan out is limited
– if it is has few, consumes too much power
• So, replace it with a transistor
– same trick in CMOS

35. How?
• When we need a large resistance we turn off
the transistor
• When we need a low resistance we turn it on

37. Schottky
• A Schottky diode is a junction between
aluminum and silicon
• Has only .4 Volt when conducting
• Can be used to prevent a transistor from
going into saturation

42. FET
• Field Effect Transistor
– Junction FET
– Metal Oxide Semiconductor FET
• The gate (base) is insulated
• High fan out with little power consumption
• Can be miniaturized to death

43. How it looks
• P-channel has p-doped source (emitter) and
drain (collector)
• Embedded in n-doped substrate
• The opposite for n-channel

45. Problem
• The substrate is part of the transistor
• Which means that one can have only one
type transistors in the circuit
• So we cannot do totem pole easily (we need
resistors)
• Resistors are half open transistors

48. Solution
• Complementary MOS
• Have “islands” of p- or n-doped substrate
• Totem pole is really easy
• So is tristate

51. Transmission Gates
• Easy to build “gates”
• Either connect or disconnect a circuit
• Can be used to implement logic