M4_Design Procedure and Combinational Logic Flashcards
Uses bipolar transistor as the principal circuit element
Transistor-transistor Logic (TTL)
Based on bipolar transistors
Transistor-transistor Logic (TTL)
Widely used families for small-and-medium-scale devices- rarely used for VLSI
Transistor-transistor Logic (TTL)
Uses the field-effect transistor as the principal circuit element
Complementary Metal Oxide Semiconductor (CMOS) Integrated
Widely used for large-scale devices
Complementary Metal Oxide Semiconductor (CMOS) Integrated
Combines HIGH SPEED with LOWER POWER CONSUMPTION
Complementary Metal Oxide Semiconductor (CMOS) Integrated
Use the bipolar transistors configured as a differential amplifier
Emitter Couple Logic (ECL) Integrated
Based on bipolar transistors, BUT removes of storage time by preventing transistors from saturating
Emitter Couple Logic (ECL) Integrated
Very fast operation-propagation delays of 1 ns or less
High power consumption, perhaps 60 Mw/gate
Emitter Couple Logic (ECL) Integrated
Sometimes referred to as fan in or fan out
Drive capabilities
Number of inputs of a logic family that can be driven by a single output
Specified the number of standard loads that can be connected to the output of the gate without degrading its normal operation
Fan out
Fan out formula to know the number of gates that can be connected to the output
(Output High/input high)=(Output low/input low)=no of gates
- It is the load an input places on an output
Fan in
- Has to do with the “speed” of the logic element
- LOWER **: means higher speed which is desirable
- Average transition delay time for the signal to propagate from input to output when the binary signal changes in value
Propagation Delay
- As propagation delays INCREASE, power consumption and heat generation INCREASE
Power Dissipation
- Maximum noise voltage added to an input signal of a digital circuit that does not cause an undesirable change in the circuit output
- Expressed in volts and represents the maximum noise signal that can be tolerated by the gate
Noise Margin
-easier to fabricate transistor than diodes
-When DIODES are required, transistors are used
Changing DTL to TTL
Anode of the input diodes are common
TTL: Multi Emitter Transistor
remaining changes in the evolution from DTL to TTL made to achieve increased speed
TTL Increase Switching Speed
Limiting transition speed which is called capacitive load, consisting of the capacitances of the reversed-biased diodes of the fan-out gates and any stray wiring capacitance
TTL Collector Capacitance
- STANDARD TTL output config with HIGH output and a LOW output transistor
○ Only one of which is active anytime- A PHASE SPLOTTER TRANSISTOR controls which transistor is active
TOTEM POLE OUTPUT
- Three possibe output states: Logic HIGH, logic LOW, and a high-impedance state(z)
- Created with circuitry to cut off both totem pole Output resistors
Tristate Output
- Much more difficult logic family around whuch to design a digital system
- Maybe faster than most application require
- Used in supercomputers like CRAY, FUJITSU and NEX and in specialist computing systems such as SGI
- Operates on the principle of current switching
Emitter Coupled Logic
- Non-saturated digital logic family
- Propagation rate as low as 1-2 ns
- Used mostly in high speed circuits
- Noise immunity and Power dissipation is the worst of all logic families
- High level -0.8V, low level -1.8V
Emitter Coupled Logic (ECL)
