Non-inverting Amplifier - Operational Amplifier

In non-inverting amplifier configuration input voltage(V_IN) is applied at the non-inverting input terminal of  an op-amp. The feedback is applied at the inverting input terminal drawing current from the output through a potential divider network. This is shown in the following circuit diagram. 

The gain of the non-inverting amplifier can be derived by applying the concept of virtual ground and Kirchoff Current Law at inverting and non-inverting terminals as follows.

Applying KCL at node V_- and taking the fact that virtually no current flows into the op-amp,

Applying the concept of virtual ground,

                                                                                          

But ,

Therefore, 

Substituting Equation (2) in Equation (1),

Therefore voltage gain A_V of the non-inverting amplifier is given by,

Instrumentation Amplifier - Op Amp

Instrumentation amplifier is a type of differential amplifier with input buffer stages. Input buffer stages aids in impedance matching with the previous stage. Instrumentation amplifiers are generally used in industrial and scientific measurements. Instrumentation amplifier has such useful features as low offset voltage,high CMRR,high input impedance, high gain etc. The circuit diagram of an instrumentation amplifier is shown below,

The above circuit produces an output voltage  (V_out)  proportional to the difference between input voltages((V₁-V₂).In the circuit diagram two op amps are shown as input buffers. But gain of the input buffers is not unity due to the presence of resistances R₁ and R_g. Op amp at the output stage is wired as a standard differential amplifier.R₂ is the input resistor and R₃ is connected from output of the output op-amp to its inverting input of the op amp. 

The voltage gain of the instrumentation amplifier is given by the expression, 

Voltage Gain G = (V_O/(V₁-V₂)) = (1+2R₁/R_g)(R₃/R₂)

Instrumentation amplifiers are used where high sensitivity, accuracy and stability are required.High gain accuracy can be achieved by using precision metal film resistors for all the resistances.

As high negative feed back is employed, the instrumentation amplifier has a good linearity. The output impedance is typically in the range of few milli ohms.

UNIT V - SPECTROSCOPY FULL NOTES

Click HERE to download Spectroscopy Full Notes as a PDF.

ANALOG ELECTRONICS - III INTERNAL TEST

Analog Electronics - 4BPH5C1

 III Internal Test

Time : 2.5 Hrs                                                                                                                         Marks: 40

                                                                        PART - A                                                        5 x 2 = 10

1.What is negative feedback?

2.State Barhausen criterion for obtaining sustained oscillations in oscillators. 

3.List out the characteristics of an ideal Op Amp.

4.Draw the symbol of an Op Amp.

5.Define CMRR.

                                                                       PART - B                                                      2 x 5 = 10

6.Explain a push-pull amplifier with a neat circuit.
7.Explain an op-amp non inverting amplifier with neat circuit diagram.

                                                                         PART - C                                                     2 x 10 = 20

8.Explain the working of a Hartley oscillator.
9.Explain an op-amp integrator and differentiator with necessary wave forms. 

Differences between Fresnel and Fraunhofer Diffractions

Fresnel  Diffraction	Fraunhofer Diffraction
The source and the screen are at finite distance from the diffracting aperture	The source and the screen are at infinite distance from the diffracting aperture
Near field diffraction	Far field diffraction
The wave fronts are divergent and are either spherical and cylindrical	The wave fronts are planar which is realized by using convex lenses
No mirror or lenses are used for observation	Diffracted light is collected by lens as in a telescope