January 2015 ~ Electronic Engineer

Thursday 22 January 2015

Logic Gates

LOGIC GATES

A logic gate is an elementary building block perform a basic logic function of a digital integrated circuit. Mostly logic gates take two binary inputs( 0 or 1 ) and give one output in 0 or 1. Boolean functions may be practically implemented by using electronic gates.

Truth Table:

Truth table help us to understand the function of logic gate, it shows the behavior and inputs of logic gate relate to its output.

This is the way to understand how to make a truth table.

TYPES OF GATES:

There are seven types of logic gates which are listed below.

AND
OR
NOR
NAND
XOR
XNOR
NOT

AND:

The AND gate is like a binary multiplication, if we say 0 is false and 1 is true then the gate acts as a logical AND operator.
AND gate is an electronic logical gates that give output high only when both k inputs are high. A dot(.) is used to show AND operator. (input 1 . input 2)

Here is a symbol and truth diagram of AND gate which helps us to understand easily.

Input 1	Input 2	Output
0	0	0
0	1	0
1	0	0
1	1	1

OR

OR gate is simply the addition of binary numbers (0 and 1) .

The OR gate is an electronic logical gate that gives a high output (1) if one or more of its inputs are high. A plus (+) is used to show the OR operation. (input 1 + input 2)

Input 1 Input 2 Output

0 0 0

0 1 1

1 0 1

1 1 1

NOR

This is a NOT-OR gate which is equal to an OR gate followed by a NOT gate. The outputs of all NOR gates are low if any of the inputs are high.

The symbol is an OR gate with a small circle on the output. The small circle represents inversion.

Input 1 Input 2 Output

0 0 1

0 1 0

1 0 0

1 1 0

NAND

This is a NOT-AND gate which is equal to an AND gate followed by a NOT gate. The outputs of NAND gates are low if both the inputs are high.
NAND gate is known as universal gate; from this gate we can make other gates.

The symbol is an NAND gate with a small circle on the output. The small circle represents inversion.

Input 1 Input 2 Output

0 0 1

0 1 1

1 0 1

1 1 0

XOR

The 'Exclusive-OR' gate is a circuit which will give a high output if either, but not both, of its two inputs are high. An encircled plus sign (

) is used to show the EOR operation.

Input 1 Input 2 Output

0 0 0

0 1 1

1 0 1

1 1 0

XNOR

The 'Exclusive-NOR' gate circuit does the opposite to the XOR gate. It will give a low output if either, but not both, of its two inputs are high. The symbol is an XNOR gate with a small circle on the output. The small circle represents inversion

Input 1 Input 2 Output

0 0 1

0 1 0

1 0 0

1 1 1

NOT

Not gate is also known as invertor gate. It inverse the binary input as 0 is OFF then it give 1 as ON from output.

This is only a logical gate that have only one input.

Input	Output
1	0
0	1

200 transistor circuit

01:11 E-book No comments

200 TRANSISTOR CIRCUITS

DOWNLOAD

POWER SUPPLY BY USING LM317

11:10 Basic Electronic 2 comments

POWER SUPPLY BY USING LM317

Introduction:

We have made 30 Volt 5 Amp regulated power supply. It can be used to charge different types of batteries and home appliances.

Circuit Diagram of Variable Voltage Regulated Power Supply:

Working:

Steps involved in making a Power Supply :

· Transformer

· Rectifier

· Filtering

· Regulator

A step-down transformer is used to reduce the dangerously high voltage to a safer level.
Bride Rectifier, Converts the AC voltage to DC, available in the form of packages of combination of four diodes forming a bridge. Bridge Rectifier output is obtained from the (+) and (-) marked terminals.
Filtering is technique in which a pure DC is obtained. The output of a bridge rectifier is not a pure DC and needs to be converted into pure form.A capacitive circuit is used as a filter or a smoother it converts the pulsating DC into a pure DC with a little ripples.
Regulator eliminates ripple by setting DC output to a fixed voltage. Voltage regulator ICs are available with fixed( typically 5,12 and 15V ) or variable output voltages. We used LM 317.
The output is shown through Digital volt meter & Analog Ampere meter.

Components used in the circuit listed below:

One 3×5" perf-board
LM317 variable voltage regulator
BR805D Bridge Rectifier
120 VAC to 24 VDC transformer
Power cable
One 2200 microfarad capacitors
One 0.1 microfarad capacitor
One 100 ohm resistor
One 5k ohm variable resistor

CONCLUSION:

The power supply is used to convert AC voltage to DC voltage for suitable appliances . The LM 371 variable voltage regulator is used for desired output and the final DC output is not a straight line but a small ripple line.