05-03-2013, 11:06 AM
OPERATIONAL AMPLIFIER(PHE-10)
AMPLIFIER.ppt (Size: 731 KB / Downloads: 40)
Op amp Comparator
Open loop gain of op amp is defined as:
AOL = Vo / VD
where VD = VNI – VINV
Open loop gain of op amp is very high (ideally infinite).
Any small difference between VNI and VINV results into saturation of output voltage ±VSAT
i.e. for VNI < VINV output is – VSAT and
for VNI > VINV output is + VSAT
Value of VSAT is limited by the supply voltage of op amp
Important features of Op Amp
High open loop gain (ideally infinite) which implies that even the smallest difference between the two inputs results into saturated output voltage
High input impedance (ideally infinite) implies that there is no current flowing into the input of an op amp
Virtual Ground
These two conditions give rise to VIRTUAL GROUND, where the voltages at both the inputs are maintained at exactly same level.
To achieve this condition, a feedback circuit between the output and the inverting input terminal of the op amp is necessary.
This results into many applications of op amp, which qualify it to be OPERATIONAL: adder, subtractor, multiplier, divider etc.
Summary
Op amp can be used for various (mathematical) operations like addition, subtraction, multiplication, division, differentiation, integration etc.
Infinite open loop gain and infinite input resistance give rise to VIRTUAL GROUND
Op amp is available in a simple to use IC form which require dual supply
Many other applications can be implemented using op amp