University of ABC, EE 101: Detailed Comparison of TTL and CMOS Devices

This report provides a comparative analysis of TTL and CMOS devices, essential components in digital electronics. It begins with an introduction to both TTL (Transistor-Transistor Logic) and CMOS (Complementary Metal Oxide Semiconductor) devices, highlighting their fundamental differences. The report then delves into a detailed comparison, examining key aspects such as noise margins, power consumption, output drive current, and the types of logic gates used. It also contrasts the 74HC and 4000 series, discussing their voltage ranges and suitability for different applications, including battery-operated systems. Furthermore, the report explores the fan-out capabilities of both CMOS and TTL, and the various configurations of TTL output. The report concludes by summarizing the advantages of CMOS in terms of lower power consumption, while also noting its increased power consumption with higher clock speeds and its susceptibility to electrostatic discharge. The report references several sources to support its findings.

Running head: - COMPARISION OF TTL AND CMOS DEVICES
COMPARISION OF TTL AND CMOS DEVICES
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1COMPARISION OF TTL AND CMOS DEVICES
Introduction
The term TTL refers to Transistor-Transistor logic. The TTL is the combination of
various transistors in a way that it can be used as logic gates. Transistors are mostly present in
complex devices. The term CMOS refers to Complementary Metal Oxide Semiconductor.
One of the best advantage of CMOS is that it can change from high to low and from low to
high (Kimber 2016). The basic difference between CMOS and TTL devices are discussed in
this report. The difference are CMOS devices use Field Effect Transistors on the other hand
TTL uses Bipolar junction transistors.
Comparison Between CMOS and TTL devices
The noise margin of TTL is 0.3 when it is high and it is 0.5 when it is low.
Comparatively the noise margins of CMOS are 0.3Vcc (Senthinathan and Prince 2013). The
power consumption of TTL is comparatively high and for CMOS the power consumption is
dependable on the Vcc frequency. The nature of output drive current for TTL is Asymmetric
in nature. The value of the high state is in the range of 0.4-2mA and the low state range from
8-20mA. On the other hand, the nature of the CMOS output drive current is symmetric in
nature. The basic gate for CMOS is the NAND and NOR gate, in case of the TTL the logic
gate is NAND. The fan out for CMOS is less than 50 and that for TTL is 10.
When it comes to comparison between the two series 74HC and 4000 series is that the
74HC series operates at a limitable voltage range. On the other hand, it is seen that CD4000
series operates on the maximum voltage of around 18 volts. However due to this reason it is
suggested to use the CD4000 series for battery operated system (Kumar 2014.). The 4000 can
run between the range of 3V-15V. Comparatively the 7400 series which is based fully on
TTL requires supply ranging from 2V-6V. The 7400 series is faster than the 4000 series.

2COMPARISION OF TTL AND CMOS DEVICES
The TTL gate comprises of three different kinds of configuration related to the output.
The configurations are the open collector, bi state and tristate. The CMOS and TTL
comprises of different series of gates and variants. The CMOS is used in the 74HC and in the
74HCT series. In case of 74HC the supply fluctuates from the range of 2-6V on the other
hand the 74HCT requires regulated and continuous power supply that is 5V. The 74HC has
high impedance. The TTL family is also categorized into different series. The programmable
logic of the TTL is based on the quad 2-input which are related to all the basic gates. The
supply requirement is 5V and 0.25V and the supply need to be smooth. The input is high if
the logic is ‘1’ and the input is low at the logic level ‘0’. The output of the TTl can sink up to
16mA. The fan out is strong enough and can drive up to 10 numbers of 74LS inputs and even
greater number of 74HCT inputs (Chang 2013).
Conclusion
It is concluded that CMOS device consumes less power compared to the TTL device.
As the clock increases the power consumption of the CMOS increases compare to that of the
TTL. When the current drawn is less the requirement of the power is also less and which
eventually lead to a simple and cheap design of the device. The CMOS devices are more
prone to damages from the electrostatic discharge compare to that off TTL components.

3COMPARISION OF TTL AND CMOS DEVICES
References
Senthinathan, R. and Prince, J.L., 2013. Simultaneous switching noise of CMOS devices and
systems (Vol. 249). Springer Science & Business Media.
Kumar, A.A., 2014. Fundamentals of digital circuits. PHI Learning Pvt. Ltd..
Chang, A.W.C., SCHOTTKY LSI Inc, 2013. Super CMOS devices on a microelectronics
system. U.S. Patent 8,476,689.
Kimber, W., 2016. Practical Digital Electronics for Technicians. Elsevier.