{| ! CMOS ! TTL | CMOS has good packing density. TTL takes up more space CMOS has better noise immmunity. TTL has a smaller noise immunity range CMOS has a large fan out. TTL can power less inputs CMOS consume less power. TTL use more power CMOS are highly static sensitive. TTL IC's tend to be less susceptible to static electricity CMOS uses FETS (Field-Effect Transistors) TTL uses BJTs (Bipolar junction Transistors CMOS can run with a range of supply voltages. TTL IC's run with a 5V supply. CMOS uses Vdd and Vss for it's power connections TTL uses BJTs (Bipolar junction Transistors CMOS takes a lot less power and is therefore suitable for battery applications, but generally speaking can't run as fast. TTL devices can drive more power into a load. CMOS chips can be damaged by static electricity: even a static jolt that you or I can't feel might destroy a CMOS chip! |}
TTL is less sensitive to static-discharge failure and less expensive. It is also faster. There is a condition called "latch up" that can happen with CMOS circuits if an overvoltage is applied during operation, so you have to design the input/output buffers to suit the operating conditions, like if a wire is attached. The first commercial applications of CMOS were by a company called Integrated Device Technology (IDT). Strangely enough, the singular advantage at that time was that CMOS allowed Hewlett Packard to create a practical calculator that was able to retain its memory registers when powered down. (Power was maintained to the chip, but the chip clock was stopped, and the chip could retain its state on very low power.) Before that though, the U.S. Navy used CMOS to reduce the size of circuits jammed in the nose cones of missiles so they could pack them with more explosives instead. TTL (Transistor-Transistor Logic) uses a different type of transistor (bipolar) whereas CMOS uses MOSFETs (metal oxide semiconductor field effect transistor). FETs don't have current flowing into the "gate" when static, whereas bipolars do (into the "base"), so generally this allows them to operate with lower power especially in a stand-by type of state. Before CMOS there was NMOS, which used N transistors and resistors. It's a bit complicated to explain in lay terms without a decent diagram, but CMOS stands for "Complimentary MOS" and uses a P transistor in place of the resistor. The advantage here is no static current flow is required, only at switching. Bipolar or TTL can in fact be faster, although it's not an apples-to-apples comparison because there are different processes for each. Some hybrids have been created like "BiCMOS," where both are combined on one chip. This is probably a lot more than you wanted to know. In short, CMOS is many things, but with the huge amounts of money invested in CMOS today it obviously has all the advantages necessary to be the default technology for most integrated electronics. * Other contributors say: CMOS logic has advantage of having smaller dimensions with new coming (usually smaller) technologies. Thus, the RC constant (RC defines transition time, where R = resistance is coming from R-ON resistance and C = capacitance is coming from gate capacitance) is smaller. Smaller RC constant means shorter transition (0->1 or 1->0)time. Logic is faster and can do more in same time (provided faster system clock). Same functionality is having smaller silicon area and this also means lower price for same functionality. Therefore the CMOS is very popular today and widely used. Concerning the ESD, yes CMOS is more sensitive, because breakdown of MOS gate is always destructive while impact of junction breakdown still depends on ESD pulse energy. Nevertheless, low-voltage CMOS is relatively easy to protect and our company has standard of 4kV ESD HBM (human body model) susceptibility as minimum. I do not remember problems after hand manipulation in the lab.
Power:- TTL 5v, CMOS 1.8 to 15v. TTL much more power hungry than CMOS. CMOS more susceptible to static than TTL. CMOS power required is small especially when static and increases with clocking frequency. TTL threshold levels < 0.8V low, >2.4V high. CMOS threshold levels < 50% of rail low, >50% high, therefore greater noise immunity.
The comparison between the CMOS and TTL logic families are as follows:
property TTL CMOS
power consumption High:20mw Low:1mw
Operating current High:mA range Low micro-ampere range
Power supply 5v+ or -0.25vdc 3v to 15vdc
Switching speeds Fast:10ms Slow :100ns
Input impedance Low High
fan-out 10 50
Transistor Transistor Logic. Main feature is cheap and old technology. Drawbacks it has limited speed and fan IN-OUT.
CMOS is the little battery in the computer's motherboard which keeps the computers internal clock running.
A digital circuit composed of bipolar junction transistors (BJTs). Widely used in all variety of electronic applications, especially prior to CMOS circuits becoming popular, TTL superseded the earlier RTL (resistor-transistor) and DTL (diode-transistor) logic designs, which used more power. In TTL, transistors are used to both isolate inputs and perform the logic switching. A "TTL" designation on a circuit input or output indicates a digital circuit rather than analog.Read more: transistor-transistor-logic-electronics
please tell about the BULK and its role in the fabrication of CMOS ?
TTL 74 86 series or CMOS 4030
CMOS logic families tolerate low temperatures because they are designed to. I suppose the why is not public because those would be trade secrets.
CMOS and NMOS are two logic families. As the name itself indicates, CMOS is complementary Metal Oxide Semiconductor technology. It uses both PMOS and NMOS transistors for design. Whereas, NMOS logic family uses only NMOS FETs for design.
Cmos logic family, because it has no resistors attached who consume active power.
The blocks in a logic gate depends on the logic family we use.A logic gate is designed using a specific logic family. The logic families can be DTL, TTL, CMOS etc.The blocks are different for different logic families.The various blocks in various logic families are:Diode logic: diodes and resistorsDTL logic : diodes and resistorsTTL logic : transistors and resistorsNMOS logic: only NMOS FETsPMOS logic: Only PMOS FETsCMOS logic: Both NMOS and PMOS FETsBiCMOS Logic: both transistors and FETs.
The switching time (on and off) of the TTL logic gate is very fast in comparison with CMOS logic gate. However, they could not tolerate higher range of power supply.
cmos
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CMOS (complementary metal oxide semi conductor) is a logic family. A logic family refers to the way of implementing logic. Using this technique, logic gates are realized. The combination of several logic gates forms a digital circuit or integrated circuit (IC). A mother board is also an IC. The technique used to realize it is CMOS logic.
because its a balanced device
CMOS is a type of technology for constructing integrated circuits. One advantage of this setup is less waste heat compared to NMOS logic or transistor-transistor logic.
The logic functions for both families of devices are the same. They differ only in their performance and other characteristics. TTL stands for Transistor-Transistor Logic. Advantages include higher speed, better current handling and relative immunity to static discharge. Disadvantages include more power consumption, output high voltage drops and fixed supply voltages (typically 5 volts). CMOS stands for Complimentary Metal Oxide Semiconductor. Advantages include better voltage output, better input voltage tolerance, variable supply voltages, higher density and much lower power consumption (although this increases with frequency). Disadvantages include sensitivity to static electricity and less current handling capability. Most new product development is in the CMOS family due to its more desirable characteristics. TTL and CMOS families contain many "sub-families" designed with special characteristics for specific applications. For instance, some CMOS families can handle greater current, function at higher speeds or operate at much lower voltages. Texas Instruments has more than 40 families of products under CMOS and TTL.
One standard load is the load of a typical input of a specified logic family. This is more relevant with bipolar logic families (e.g. RTL, DTL, TTL, ECL, I2L) than MOS logic families (e.g. NMOS, CMOS). Outputs of devices in these logic families are then rated by the number of standard loads they can drive. However when crossing between logic families (e.g. LS TTL to S TTL) the concept of standard loads is less useful and actual high/low state input current loading and output drive capability calculations should usually be made.