28 March 2020

Difference between CMOS and TTL | CMOS Vs TTL logic

CMOS stands for complementary metal-oxide-semiconductor is also another classification of ICs that uses the Filed effect transistor in the design. TTL stands for Transistor transistor logic. It is a classification of integrated circuits. The name is derived from the use of two bipolar junction transistors or BJT in the design of each logic gate. TTL chips tend to consume a lot more power compared to CMOS chips, especially at rest. As we know that the power consumption of a CMOS chip can vary depending on a few factors. Here this article gives the difference between CMOS and TTL to better understand this topic.

Related article: NMOS Vs CMOS

The main key difference between CMOS and TTL are listed below:

CMOS Vs TTL logic: 

  • CMOS stands for Complimentary Metal-oxide Semicodictor while in TTL stands for Transistor-Transistor Logic.
  • CMOS circuit uses a field-effect transistor by connecting NMOS and PMOS, while the TTL circuit uses a bipolar junction transistor.
  • The design of the CMOS can be considered to be very simpler as compared to the TTL. 
  • The longer rise and fall times of the CMOS can make this more energy-efficient as compared to the TTL.
  • CMOS is to be weaker than TTL when it is at rest.
  • CMOS components are generally more expensive when compared to TTL components, nit on system level, the CMOS chip are less expensive as there are smaller in size as compared to the TTL chips.
  • A single logic gate in a CMOS chip can consist of as little as two FETs while a logic gate in a TTL chip consists of a substantial number of a part as extra components like resistors are needed.
  • CMOS circuit is used in NAND-NOR gates while the basic gate use in standard TTL are NANA gates.
  • There are substantial differences in the voltage level range for both. For TTL it is 4.75 to 5.25 V while for the CMOS it ranges between 0 to 1/3 VDD at a lower level and 2/3 VDD to VDD at high levels.
  • Fan out of standard loads that can be connected to the output of the gate under normal for TTL is while it is 50 for CMOS circuit.
  • CMOS circuits have better noise immunity than TTL circuits.
  • The electromagnetic disruptions CMOS circuit components are more sensitive as compared to the TTL logic components.
  • CMOS chips will be more likely to get damaged easily as compared to the TTL.
  • The power consumption of CMOS can increase faster as compared to TTL whenever needed.
  • A single gate in a CMOS chip can consume around 10nW while an equivalent gate on a TTL chip is consumed around 10mW of power.
  • There are propagation delays present in both, On average the propagation delays of TTL are usually on 10nS whereas the propagation delays for the CMOS lay between 20 to 50 ns.
  • CMOS technology and its circuit are more economical and preferred more as compared to TTL logic.
  • CMOS is more susceptible to damage from electrostatic discharge than TTL components.
  • The number of standard inputs that can be connected to the gate is the fan which is approximately 12-14 for the TTL and for the CMOS it is 10 only.
In this article, we have to discuss the difference between CMOS and TTL.  I hope by reading this article you have gained some basic information about this article. If you have any queries regarding this article or to implement any electronics or electrical project please feel free to comment in the below section.

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