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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING
SUBJECT CODE: EC1203
DIGITAL ELECTRONICS
(FOR THIRD SEMESTER ECE)

TWO MARK QUESTIONS-ANSWERS

PREPARED BY
Y.IREANEUS ANNA REJANI (AP/ECE)

Noorul Islam College of Engineering, Kumaracoil
Department of Electronics & Communication
Third semester
EC1203 Digital Electronics

Part - A
Unit – 1

1. Define binary logic?
Binary logic consists of binary variables and logical operations. The variables are designated by the alphabets such as A, B, C, x, y, z, etc., with each variable having only two distinct values: 1 and 0. There are three basic logic operations: AND, OR, and NOT.

2. What are the basic digital logic gates?
The three basic logic gates are
AND gate
OR gate
NOT gate
3. What is a Logic gate?
Logic gates are the basic elements that make up a digital system. The electronic gate is a circuit that is able to operate on a number of binary inputs in order to perform a particular logical function.

4.Give the classification of logic families
Bipolar

Saturated

RTL
ECL
IIL
TTL

Non Saturated

Unipolar

PMOS
NMOS
CMOS

Schottky TTL
DTL

5. Which gates are called as the universal gates? What are its advantages? The NAND and NOR gates are called as the universal gates. These gates are used to perform any type of logic application.
6.Classify the logic family by operation?
The Bipolar logic family is classified into

Saturated logic
Unsaturated logic.
The RTL, DTL, TTL, I2L, HTL logic comes under the saturated logic family. The Schottky TTL, and ECL logic comes under the unsaturated logic family. 7.State the classifications of FET devices.
FET is classified as
1. Junction Field Effect Transistor (JFET)
2. Metal oxide semiconductor family (MOS).
8.Mention the classification of saturated bipolar logic families. The bipolar logic family is classified as follows:
RTL- Resistor Transistor Logic
DTL- Diode Transistor logic
I2L- Integrated Injection Logic
TTL- Transistor Transistor Logic
ECL- Emitter Coupled Logic
9. Mention the important characteristics of digital IC’s?
Fan out
Power dissipation
Propagation Delay
Noise Margin
Fan In
Operating temperature
Power supply requirements
10. Define Fan-out?
Fan out specifies the number of standard loads that the output of the gate can drive with out impairment of its normal operation.
11. Define power dissipation?
Power dissipation is measure of power consumed by the gate when fully driven by all its inputs.
12. What is propagation delay?
Propagation delay is the average transition delay time for the signal to propagate from input to output when the signals change in value. It is expressed in ns. 13. Define noise margin?
It is the maximum noise voltage added to an input signal of a digital circuit that does not cause an undesirable change in the circuit output. It is expressed in volts. 14. Define fan in?
Fan in is the number of inputs connected to the gate without any degradation in the voltage level.
15. What is Operating temperature?
All the gates or semiconductor devices are temperature sensitive in nature. The temperature in which the performance of the IC is effective is called as operating temperature. Operating temperature of the IC vary from 00 C to 700 c.

16.What is High Threshold Logic?
Some digital circuits operate in environments, which produce very high noise signals. For operation in such surroundings there is available a type of DTL gate which possesses a high threshold to noise immunity. This type of gate is called HTL logic or High Threshold Logic.

17. What are the types of TTL logic?
1. Open collector output
2. Totem-Pole Output
3. Tri-state output.
18. What is depletion mode operation MOS?
If the channel is initially doped lightly with p-type impurity a conducting channel exists at zero gate voltage and the device is said to operate in depletion mode. 19. What is enhancement mode operation of MOS?

If the region beneath the...
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