10-09-2013, 03:30 PM
OP-AMP 741
OP-AMP 741.pptx (Size: 235.92 KB / Downloads: 16)
INTRODUCTION
The main purpose of an op-amp is to amplify (increase) a weak signal .
The OP-AMP has two inputs, INVERTING ( - ) and NON-INVERTING (+), and one output at pin 6.
The chip can be used in a circuit in two ways.
If the voltage goes into pin two then it is known as an INVERTING AMPLIFIER.
If the voltage goes into pin three then the circuit becomes a NON-INVERTING AMPLIFIER.
An inverting amplifier:
Leg two is the input and the output is always reversed.
In an inverting amplifier the voltage enters the 741 chip through leg two and comes out of the 741 chip at leg six.
If the polarity is positive going into the chip, it negative by the time it comes out through leg six.
The polarity has been ‘inverted’.
OP-AMPS AS COMPARATORS
However, this time the 741 is used as a comparator and not an amplifier.
The difference between the two is small but significant.
Even if used as a comparator the 741 still detects weak signals so that they can be recognized more easily.
7490 DECADE COUNTER
The 74LS90 is a simple counter, i.e; it can count from 0 to 9 cyclically in its natural mode.
It counts the i/p pulses and the o/p is received as a 4-bit binary number through pins Qa,Qb,Qc &Qd.
The binary o/p is reset to 0000 at every tenth pulse and count starts from 0 again.
A pulse is also generated(probably at 9) as it resets its o/p to 0000.
The other high counts can be generated by connecting two or more 7490ICs