description of digital IC

1. DIGITAL IC

2. What is Logic Family?
 Group of logic gates having compatible logic levels
and power supply characteristics.
 Set of techniques used to implement logic within
VLSI integrated circuits

3. Logic Families
 Resistor–transistor logic (RTL)
 Diode–transistor logic (DTL)
 Emitter-coupled logic (ECL)
 Transistor–transistor logic (TTL)
 P-type metal–oxide–semiconductor logic (PMOS)
 N-type metal–oxide–semiconductor logic (NMOS)
 Complementary metal–oxide–semiconductor logic
(CMOS)
 Bipolar complementary metal–oxide–semiconductor
logic (BiCMOS)
 Integrated injection logic (I2L)

4. Basic Concepts
 Fan In: Maximum no. of inputs of gate
 Increase in fan in increases gate delay
 Fan out: Maximum no. of outputs gate can drive
 The fan-out really depends on the amount of electric
current a gate can source or sink while driving other
gates.
 Increase in fan out can affect noise margin, operating
temperature, rise time, fall time and propagation
delay.

5. Basic Concepts
 Gate delay
 Delay offered by a gate for the signal appearing at
its input, before it reaches the gate output.
 Also known as propagation delay.
 Wire Delay
 Delay offered by interconnection between gates
 Also known as interconnect delay

6. Basic Concepts
 Skew
 The same signal arriving at different parts of the
design with different phase is known as skew.
 Normally refers to clock signals

7. Basic Concepts
 Logic levels
 VOHmin : The minimum output voltage in HIGH state (logic
'1'). VOHmin is 2.4 V for TTL and 4.9 V for CMOS.
 VOLmax : The maximum output voltage in LOW state (logic
'0'). VOLmax is 0.4 V for TTL and 0.1 V for CMOS.
 VIHmin : The minimum input voltage guaranteed to be
recognised as logic 1. VIHmin is 2 V for TTL and 3.5 V for
CMOS.
 VILmax : The maximum input voltage guaranteed to be
recognised as logic 0. VILmax is 0.8 V for TTL and 1.5 V for
CMOS.

8. Basic Concepts
 Current levels
 Source and sink capability
 Noise Margin
 Low noise margin (LNM) = VILmax-VOLmax
 High noise margin (HNM) = VOHmin-VIHmin
 Rise time (tr)
 Fall time (tf)
 Propogation delay (tpd)
 The time between the logic transition on an input and the
corresponding logic transition on the output of the logic
gate.

9. Basic Concepts
 Power dissipation
 Static
power dissipation
 Dynamic power dissipation

10. Logic Thresholds And Outputs For
Different Logic Families
 The term threshold is used to specify the voltage in
which an electrical signal is determined to be a 1 or
0”

11. Gate Transition Times And Current Sink
Capability For Different Logic Families

12. Practical digital signal

13. Thank You