What is the difference between the TTL chips and CMOS chips?

TTL is considered to be less used today when considering cost , functionality and reliability  on CCTV systems .

CMOS seems to be more robust yet TTL is cheaper and initially faster than CMOS  .

Industry seems to have chosen CMOS more frequently over the years particularly since the speed of CMOS has advanced over the years ..It is similar to buying a car ..we ask ourselves the question ..do we judge the speed on how fast it starts up or on how long it can run at a high speed .

Characteristics of CMOS logic:

• Dissipates low power: The power dissipation is dependent on the power supply voltage, frequency, output load, and input rise time. At1 MHz and pF load, the power dissipation is typically nW per gate.
• Short propagation delays: Depending on the power supply, the propagation delays are usually around nS to nS.
• Rise and fall times are controlled: The rise and falls are usually ramps instead of step functions, and they are -% longer than the propagation delays.
• Noise immunity approaches% or% of the full logic swing.
• Levels of the logic signal will be essentially equal to the power supplied since the input impedance is so high.
• Voltage levels range from0 to VDD where VDD is the supply voltage. A low level is anywhere between0 and1/3 VDD while a high level is between2/3 VDD and VDD.

Characteristics of TTL logic:

• Power dissipation is usually mW per gate.
• Propagation delays are nS when driving a pF/ ohm load.
• Voltage levels range from0 to Vcc where Vcc is typically4.V -5.V. Voltage range0V -0.8V creates logic level0. Voltage range2V - Vcc creates logic level1.

CMOS compared to TTL:

• CMOS components are typically more expensive than TTL equivalents. However, CMOS technology is usually less expensive on a system level due to CMOS chips being smaller and requiring less regulation.
• CMOS circuits do not draw as much power as TTL circuits while at rest. However, CMOS power consumption increases faster with higher clock speeds than TTL does. Lower current draw requires less power supply distribution, therefore causing a simpler and cheaper design.
• Due to longer rise and fall times, the transmission of digital signals becomes simpler and less expensive with CMOS chips.
• CMOS components are more susceptible to damage from electrostatic discharge than TTL components.

TTL chips are typicalling less expensive than CMOS components. However, on system level CMOS is less expensive and it needs less regulations. TTL circuits needs huge power when compared with CMOS. CMOS components are liable to damage from electrostatic discharge than TTL.

CMOS components are typically more expensive than TTL equivalents. However, CMOS technology is usually less expensive on a system level due to CMOS chips being smaller and requiring less regulation

TTL (Transistor-Transistor Logic) is a name for type of logic circuits which are constructed using the bipolar transistors. In general the bipolar transistors such as the NPN and PNP transistors are current operated devices. In these types of transistors, when used for digital logic circuits, typically the input voltage is applied across the Base-Emitter junction. As a result of this a small base current is produced in that junction. This small base current is magnified by the transistor's current gain factor B(called Beta), resulting in a large amount of collector-emitter current. This is basiclly how a TTL switch works. The TTL family of circuits are generally very fast, but this speed comes at the cost of higher power dissipation. Also, a typical TTL logic gate circuit requires multiple transistors and other passive components such as resistors. This results in lower number of gates that can be put on an IC built using TTL family.The CMOS(Complimentary Metal Oxide Semiconductor) family of logic circuits are buit using Metal Oxide Semiconductor(MOS) Field Effect Transistors (FET). These types of transistors are voltage operated devices. A typical CMOS logic gate circuit can be constructed using as little as two MOSFET transistors (A CMOS Inverter) resulting in a much higher density of logic gates that can be put on an IC. Also, CMOS gates use much much lower power to operate compared to the TTL gates because no resistors are required to build such circuits. CMOS logic also allows much higher operating voltages compared to the TTL family. One drawback of CMOS family is that they are slower than the TTL family, however these days this may no longer be true