Why is ttl faster than cmos

The main advantage of CMOS logic family is their extremely low power consumption. This is because there is no direct conducting path from Vdd to ground in either of input conditions. The advantages are: low cost, high availability, high compatibility, ease of use.

The disadvantages are: limited speed and frequency, noisy, very high power consumption at higher frequencies. It also has a relatively high switching speed.

In Schottky TTL the low cut-in voltage of the diode limits the base-collector voltage to about mV, which prevents the transistor falling into saturation. To make sure the rise time is fast at high frequency, a large current is needed, which can be in the order of several amps at MHz or GHz frequencies. This current is consumed only when the input has to change state, unlike TTL where the bias current has to be present with the signal. TTL outputs are either totem pole or pullups.

With totem pole, the output can swing only within 0. However, the output currents are much higher than their CMOS counterparts.

Meanwhile, CMOS outputs, which can be compared with voltage controlled resistors, can output within millivolts of the supply rails depending on the load. However, the output currents are limited, often being barely enough to drive a couple of LEDs. Thanks to their smaller current requirements, CMOS logic lends itself very well to miniaturization, with millions of transistors being able to be packed into a small area without the current requirement being impractically high.

Field-effect transistors depend on a thin silicon oxide layer between the gate and channel to provide isolation between them. This oxide layer is nanometers thick and has a very small breakdown voltage, rarely exceeding 20V even in high power FETs.

This makes CMOS very susceptible to electrostatic discharge and overvoltage. Thus people often unwillingly damage their chips only by touching the terminals of the CMOS. It consumes lesser power than the TTL and is more economical as well. The output power of the CMOS is higher and it is smaller in size as well. With higher immunity to the noise, these allow lower levels of noise to transmit while the transmission of the singles.

Also, the propagation delays are smaller and thus provide faster transmission of the signals that the TTL circuits. With larger fan outnumber the number of loads can be connected at the output terminal of the CMOS circuit. Though these are delicate and therefore require care and attention while handling them. We will never spam you. What is CMOS? CMOS Working Technology Various types of Integrated circuits are constructed using the CMOS technology like the microprocessors, microcontrollers , memory chips and several other digital logic circuits.

What is TTL? Which one is Better? There are propagation delays present in both.