The document provides an overview of transistor-transistor logic (TTL) and its applications in digital circuits, detailing the evolution and variations of TTL technology since its introduction in 1963. It explains different TTL sub-families, their characteristics such as power dissipation and speed, and comparisons with other logic families like resistor-transistor logic and CMOS. Additionally, it outlines key parameters like propagation delay and speed-power product that are crucial for evaluating TTL performance.

2. Dayalbagh Educational
Institute
D.Surat
M.Sc. Physics

3. Transistor
Transistor
Logic

4. Introduction
Introduction to Digital logic
gates
Technologies
Transistor Transistor Logic
7400 TTL Series
TTL Sub-families
Two Input TTL NAND Gate
TTL Logic Levels and Noise
Margins
TTL Family Evolution
Comparison to logic families

5. Introduction to Digital logic Gates
★ A Digital Logic Gate is an electronic device that makes
logical decisions based on the different combinations of
digital signals present on its inputs.
★ Digital logic gates may have more than one input but
generally only have one digital output.
★ Individual logic gates can be connected together to form
combinational or sequential circuits, or larger logic gate
functions.

6. Technologies
★ The list of packaged building-block logic families can be
divided into categories, listed here in roughly
chronological order of introduction, along with their usual
abbreviations:
o Resistor–transistor logic (RTL)
• Direct-coupled transistor logic (DCTL)
• Resistor–capacitor–transistor logic (RCTL)

7. o Diode–transistor logic (DTL)
Complemented transistor diode logic (CTDL)
High-threshold logic (HTL)
o Emitter-coupled logic (ECL)
Positive emitter-coupled logic (PECL)
Low-voltage positive emitter-coupled logic (LVPECL)
o Transistor–transistor logic (TTL)
o P-type metal–oxide–semiconductor logic (PMOS)
o N-type metal–oxide–semiconductor logic (NMOS)

8. o Complementary metal–oxide–semiconductor logic
(CMOS)
o Bipolar complementary metal–oxide–semiconductor logic
(BiCMOS)
o Integrated injection logic (I2L)

9. Transistor - Transistor Logic
★ Transistor–transistor logic (TTL) is a class of digital
circuits built from bipolar junction transistors (BJT) and
resistors.
★ It is called transistor–transistor logic because both the
logic gating function and the amplifying function are
performed by transistors.

10. ★ The first transistor–transistor logic family of integrated
circuits was introduced by Sylvania as Sylvania Universal
High–Level Logic (SUHL) in 1963.
★ TTL manufacturers offered a wide range of logic gate, flip-
flops, counters, and other circuits. Several variations of
the original bipolar TTL concept were developed, yielding
circuits with higher speed or lower power dissipation to
allow optimization of a design.

11. ★ The design of the input and outputs of TTL gates allowed
many elements to be interconnected.
★ Transistor-transistor logic (TTL) is a digital logic design in
which bipolar transistor s act on direct-current pulses.
★ Many TTL logic gate s are typically fabricated onto a
single integrated circuit (IC).
★ TTL ICs usually have four-digit numbers beginning with
74 or 54.
★ A TTL device employs transistors with multiple emitters in
gates having more than one input.

12. 7400 TTL Series
★ TTL ICs first developed in 1965 and they are known as
“standard TTL” . This version of TTL circuit is not
available now.
★ TTL family use only transistor to perform the basic logic
operations.
★ The standard TTL is improved to a great extent over the
year.
★ TTL devices are still used as “glue” logic which connects
more complex devices in digital system.

13. TTL Sub-families
★ There are several subfamilies or series of the TTL technology
such as
★ Standard(74)
★ Low-power(74L),
★ High-speed(74H),
★ Schottky(74S),
★ Low-power Schottky(74LS),
★ Advanced Schottky (74AS),
★ Advanced low-power Schottky (74ALS).

14. Contd...
★ Commercial TTL ICs have a number designation that
starts with 74 and follows with a suffix that identifies the
series type. Examples are 7404, 74S86, and 74ALS161.
★ The speed-power product is an important parameter for
comparing the various TTL series.
★ This is the product of the propagation delay and power
dissipation and is measured in picojoules (pJ).

15. ★ The propagation delay of a transistor circuit that goes into
saturation depends mostly on two factors:
○ storage time
○ RC time constants.
★ A pulse through a gate take certain amount of time from
input to output. This interval of time is known as
propagation time.

16. Two Input TTL NAND Gate

17. Standard TTL 74 Series
★ Offer a combination of speed and dissipation suited for
many applications.
★ The 54 series is the counterpart of 74 series.

18. Low Power TTL, 74L series
★ Essentially the same basic circuit as the standard 74
series except that all resistance values (R1=40k R2=20k
R3=12k R4=500) are increased.
★ Large resistance reduce the current and therefore, the
power requirement,But at the expense of reduction in
speed.
★ The power consumption of Low power TTL is about 1/10
of that of standard TTL.

19. High Speed TTL, 74H Series
★ Essentially the same basic circuit as the standard 74
series except that smaller resistance values (R1=2.8k
R2=760 R3=470 R4=58) are used and the emitter follower
transistor Q3 is replaced by Darlington pair and emitter to
base joining of Darlington pair (Q5-Q3) is connected to
ground through a resistor of 4k.
★ The switching speed of 74H series is approximately two
times more than that of standard TTL.

20. Schottky TTL, 74S Series
★ A major slowdown factor in BJTs is due to transistors
going in/out of saturation
★ Schottky diode has a lower forward bias (0.25V)
★ When BC junction would become forward biased, the
Schottky diode bypasses the current preventing the
transistor from going into saturation.

21. Low Power Schottky TTL, 74LS Series
★ Lower power and slower speed version of 74S series.
★ It uses the schottky clamped transistor, but with larger
resistance values than those in the 74S series.

22. TTL Logic Levels and Noise Margins

23. TTL Series
Name
TTL Series
Name Prefix
Fan-Out Power (mw)
dissipation
Propagation
Delay nSec
Speed Power
Product pJ
Standard 74 10 10 9 90
Low-Power 74L 20 1 33 33
High-Speed 74H 10 22 6 132
Schottky 74S 10 19 3 57
Low Power
Schottky
74LS 20 2 9.5 19
Advanced
Schottky
74AS 40 10 1.5 15
Advanced Low
Power Schottky
74ALS 20 1 4 4

24. TTL family evolution

26. Comparison to
logic families

27. Resistor Transistor logic
★ It has a fan-out of 5.
★ Propagation delay is
25ns.
★ Power dissipation is
12mw.
★ Noise margin for low
signal input is 0.4v.
★ Poor noise immunity.
★ lLow speed.

28. Diode Transistor Logic
★ It has fan-out of 8.
★ It has high noise
immunity.
★ Power dissipation is
12mw.
★ Propagation constant is
average 30ns.
★ Noise margin is about
0.7v.

29. Emitter Coupled Logic
★ Propagation delay is
very low (<1ns).
★ ECL is fastest logic
family.
★ ECL circuit usually
operate with -ive
supplies (+ive terminal is
connected to ground).

30. Transistor Transistor
Logic
★ TTl has greater speed
than DTL.
★ Less noise immunity.
★ Power dissipation is
10nw.
★ It has fan-in of 6 and fan-
out of 10.
★ Propagation time delay
is 5-15nsec.

31. CMOS
★ Dissipates low power,
power dissipation is
typically 10 nW per gate.
★ The propagation delays
are usually around 25 nS
to 50 nS.
★ Noise immunity
approaches 50% or 45%
of the full logic swing.

32. Online Sources
www.wikipedia.com
www.allaboutcircuits.com
www.electrical4u.com
Books Refered
FUNDAMENTALS OF DIGITAL CIRCUITS
By A. ANAND KUMAR

33. Thank You...