OPERATIONAL AMPLIFIER IC 741| INVERTING MODE AND NON-INVERTING MODE

OPERATIONAL AMPLIFIER IC 741

Oper­a­tional ampli­fiers IC741 are avail­able in IC for­mat. The UA 741 is the most pop­u­lar of these. It was devel­oped by a com­pa­ny called Fairchild Semiconductor 

There are also vari­ants such as the MCI 741 op amp devel­oped by Motoro­la and the LM 741 op amp devel­oped by the Nation­al semiconductor 

It has two input ter­mi­nals, invert­ing and non-invert­ing. If a sig­nal is giv­en at the invert­ing input, the sig­nal received at the out­put will be 180 ° phase shift from the sig­nal giv­en at the input. 

That is, if a pos­i­tive sig­nal is giv­en at the invert­ing input, a neg­a­tive sig­nal is obtained at the out­put, and if a neg­a­tive sig­nal is giv­en, a pos­i­tive sig­nal is obtained at the output 

If a sig­nal is giv­en at a non-invert­ing input, the out­put sig­nal will be equal to the phase angle of the input sig­nal. That is, if a pos­i­tive sig­nal is giv­en at a non-invert­ing input, a pos­i­tive sig­nal is obtained at the out­put, and a neg­a­tive sig­nal is obtained at the out­put if a neg­a­tive sig­nal is given. 

The nature of the sig­nal received at the out­put of the oper­a­tional ampli­fi­er depends on the nature of the com­po­nents and their ver­sions that are exter­nal­ly con­nect­ed to it 

PIN DETAILS IC 741 

IC 741 is a dual in line IC pack­age with 8 pins 

PIN NO 1 : Off set null balance

PIN NO 2 : Invert­ing input

PIN NO 3 : Non invert­ing input 

PIN NO 4 : Neg­a­tive supply

PIN NO 5 : Off set null balance 

PIN NO 6 : Output 

PIN NO 7 : Pos­i­tive supply 

PIN NO 8 : NO connection 

IMPORTANT TERMS

Input Offset Voltage 

The input volt­age giv­en between the two input ter­mi­nals of the op-amp in order to bring the out­put volt­age to zero is called the input off­set voltage 

Input Bias Current 

The aver­age val­ue of the cur­rent pass­ing through the two input ter­mi­nals of an op-amp oper­at­ing in bal­ance is called the input bias current 

Input offset current

The dif­fer­ence between the cur­rents flow­ing through the two input ter­mi­nals of an op-amp oper­at­ing in bal­ance is called the input off­set current 

Output Offset Voltage

When two input ter­mi­nals of an op-amp are con­nect­ed direct­ly to ground, the volt­age at its out­put is called the out­put off­set voltage 

Differential Input Resistance

Dif­fer­en­tial input resis­tance is the resis­tance val­ue mea­sured at the next input ter­mi­nal when one of the two input ter­mi­nals in an op-amp is con­nect­ed direct­ly to ground 

Input Capacitance

When one of the two ter­mi­nals in an op-amp is con­nect­ed direct­ly to ground, the val­ue of the capac­i­tance mea­sured at the next ter­mi­nal is called the input capacitance 

Open Loop Voltage Gain

The dif­fer­en­tial volt­age gain obtained when there is no feed­back con­nec­tion in the op-amp is called the open loop volt­age gain 

Supply Voltage Rejection Ratio

The ratio between the input off-set volt­age and a pow­er sup­ply volt­age that varies accord­ing­ly (when the volt­ages of oth­er pow­er sup­plies are con­stant) is called the SVRR 

Output Voltage Swing

The out­put volt­age swing is the max­i­mum peak-to-peak volt­age that can be obtained at the out­put with­out any clip­ping on the wave­form when the DC out­put is zero 

Slew Rate

The max­i­mum out­put volt­age that varies per unit time is called the slew rate. It is denot­ed by the unit volts / microsecond 

SR = dVo/dt/maximum

V/μs

Common Mode Rejection Ratio

The ratio between dif­fer­en­tial volt­age gain (Ad) and com­mon mode volt­age gain (Acm) is called CMRR 

CMRR = Ad/Acm

Maximum Differential Input Voltage

The max­i­mum dif­fer­en­tial input volt­age giv­en to an op-amp with­out being affect­ed is called the max­i­mum dif­fer­en­tial input voltage 

Maximum Common Mode Input Voltage 

The max­i­mum volt­age that the op-amp can sup­ply to its two input ter­mi­nals before it starts oper­at­ing non-lin­ear is called the max­i­mum com­mon mode input voltage 

INVERTING MODE

The input sig­nal is fed to the invert­ing ter­mi­nal via a resis­tor called Ri. Rf is the feed­back resistor 

Con­nects the invert­ing ter­mi­nal and the out­put ter­mi­nal. Once the input volt­age Vi is giv­en, the cur­rent i pass­es through the input resis­tor Ri and the cur­rent 1 pass­es through the feed­back resis­tor Rf 

The input resis­tance val­ue of the invert­ing ter­mi­nal is high (or) so cur­rent does not flow inside the invert­ing ter­mi­nal. Also it acts as a vir­tu­al ground so its volt­age lev­el is zero 

Non Inverting Mode 

Where the input volt­age is applied direct­ly to the non-invert­ing input. The invert­ing input has a resis­tor called Ri and the feed­back has a resis­tor called Rf