We have treated the gain of the op-amp as a constant.However it is a complex number that is a function of frequency.Therefore at a given frequency the gain will have a specific magnitude as well as phase angle.The manner in which the gain of the op-amp response to different frequencies is called the frequency response.A graph of the magnitude of the gain and frequency is called a frequency plot. Share and Enjoy: read more

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In the inverting amplifier,only one input is applied and that is to the inverting input terminal.The non-inverting input terminal is grounded since V1=0V and V2=Vin. Therefore Vo = -A(Vin) The negative sign indicates the output voltage is out of phase with respect to input by 180 degree or is of opposite polarity.Thus in the inverting amplifier,The input signal is amplified by gain A and is also inverted at the output. Non-Inverting Amplifier In this configuration ,the input is given to the non inverting input terminal and the inverting terminal is connected to ground. In the circuit,V1=Vin and V2=0V therefore the output voltage Vo=AVin.This means that the output voltage is larger than the input voltage by gain A and is in phase with the input signal Share and read more

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The figure shows the open loop configuration of differential amplifier in which the input signals Vin1 and Vin2 are applied to the positive and negative input terminals since the op-amp amplifies the difference between the two input signals,this configuration is called differential amplifier.Vin1 and Vin2 could be either ac or dc voltages.The source resistances Rin1 and Rin2 are negligible compared to the input resistance Ri.The voltage drop across the resistors can be assumed to be zero,which then implies that V1=Vin and V2=Vin2.The the output voltage Vo=A(Vin1-Vin2). The output voltage is equal to the voltage gain A times the difference between the two input voltage.The polarity of the output voltage is dependent on the polarity of the input difference voltage(Vin1-Vin2).In open loop read more

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The function of the last stage in an op-amp is to supply the load current and provide a low impedance output.a simple output stage is an emitter follower with complementary transistors.When Vi is positive,transistor Q1 is on and supplies current to load RL .If Vi is negative,Q1 is cutoff and Q2 acts as a sink to remove current from the load RL .There is however,a limitation in this circuit.The output voltage VO remains zero volt until the input Viexceeds VBE(cut in)=0.5V.This is called cross over distortion.It can be eliminated by applying a bias voltage V greater than QVBE(cut in)=1V between the two bases so that a small current flows in the transistor even in the quiescent state. Share and Enjoy: read more

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There are two good reasons for using a level shifter in an IC(op-amp).As we want an op-amp to operate down to dc,no coupling capacitor is used.Because of direct coupling,the dc level rises from stage to stage.The increase in dc level tend to shift the operating point of next stage.This,in turn,limits the output voltage swing and even distort the output signal.It,therefore becomes essential to shift the quiescent voltage before it is applied to the next stage.Another requirement to be satisfied is that the output should have voltage level of 0V for input signal. he simplest type of a level shifter is shown in fig.1 given below.This is basically an emitter follower.Hence the level shifter also acts as buffer to isolate the high gain stages from output stage.The amount of shift read more

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Input Stage of an op-amp The input stage is a dual input,balanced output differential amplifier.It has 2 inputs Vin1 and Vin2 which are applied at the bases B1 and B2 of transistors Q1 and Q2.The output V0 ois measured between the two collectors C1 and C2 which are at the same dc potential.Because of the equal dc potential at the two collectors with respect to ground,the output is referred to as balanced output. Intermediate Stage The next stage is dual input,unbalanced output difference amplifier.Here two input signals are used however the output is measured at only one of the two collectors with reference to ground.The output is referred to as an unbalanced output because the collector at which the output voltage is measured is at some finite dc potential with reference to ground.In read more

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An operational amplifier is a high gain amplifier usually consisting of one or more differential amplifier and usually followed by a level translator and an output stage. The op-amp is a versatile device that can be used to amplify dc as well as ac input signal and was originally designed for performing mathematical operations such as addition ,subtraction,multiplication and integration.Thus the name operational amplifier stems from its original use for these mathematical operations and is abbreviated to op-amp.The first op-amp was introduced by Fairchild semiconductor in 1963,its μA 702 which set the stage for development of other IC op-amps Internal Block Schematic of op-amp The input stage is the dual input balanced output differential amplifier.This stage generally provides most read more

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We are now going through a period of micro electronic circuits.Micro electronics refers to the circuit technology that is capable of producing circuits that contain millions of components in a small piece of silicon(known as silicon chip)whose area is in the order of 100sq.mm.The integrated circuits or IC is a miniature, low cost electronic circuit consisting of active and passive components that are inseparably joined together on a single crystal chip of silicon.These circuits offer a number of distinct advantages over those made by the interconnecting discrete components. Advantages Miniaturization and hence increased equipment density Cost reduction due to batch production Increased system reliability due to elimination of soldered joints Improved functional performance(as it is read more

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