GATE Electronics|Electrical

A random process is defined by X(t) + A where A is continuous random variable uniformly distributed on (0,1). The auto correlation function and mean of the process is a) 1/2 & 1/3 b) 1/3 & 1/2 c) 1 & 1/2 d) 1/2 & 1 Answer: b Explanation: E[X(t)X(t+t)] = 1/3 and E[X(t)] = 1/2 respectively. GATE ELECTRONICS 2020 https://t.me/GateElectronics

If in a particular application Vgs is 10 mV, find the minimum overdrive voltage at which the transistor should be operated so that the second-harmonic distortion is kept to less than 1%. a) 1V b) 0.75V c) 0.5V d) 0.25V

What is thermal voltage drift? Ans. The average rate of change of input offset voltage per unit change in temperature is called thermal voltage drift (∆Vio /∆T). GATE ELECTRONICS 2020 https://t.me/GateElectronics

What is thermal voltage? Ans. Thermal voltage is the voltage equivalent of temperature. At 0 K, electrons in a semiconductor are at rest. If temperature is increased, the electronic gain energy proportional to temperature and this voltage can be expressed as Energy/Coulomb. GATE ELECTRONICS 2020 https://t.me/GateElectronics

How is keyboard interfaced to CPU? What is standardly used? Ans. A programmable peripheral interface (8255) is a device that interfaces a keyboard to a computer. Its main function is to inform the computer when a key is pressed or released. When the data from the keyboard arrives, the controller raises an interrupt to allow the CPU to handle the input. RS-232 serial interface is established GATE ELECTRONICS 2020 https://t.me/GateElectronics

Root Locus & Its Significance Usually the open loop gain (Let us say K) is varied. Based on the range of K. Types of  root locus are defined are :- K: (0 → ∞) Roots Locus Diagram K: (0 → –∞) Complementary Root Locus Diagram K: (–∞ → ∞) Complete Root Locus Roots locus uses the open loop transfer function to predict the closed loop stability. GATE ELECTRONICS 2020 https://t.me/GateElectronics

Mention some examples where the Thevenin's theorem cannot be applied? (IES-06) Ans. This theorem is inapplicable to loads which are magnetically coupled to other parts of the circuit. This theorem is inapplicable for non-linear and unilateral networks. To apply this theorem, the load should not contain any dependent source. GATE ELECTRONICS 2020 https://t.me/GateElectronics

Mention some examples where the reciprocity theorem is not applicable? Ans: This theorem is inapplicable to unilateral networks comprising of elector tubes or other control devices. This theorem is inapplicable to circuits with time-varying elements. This theorem is inapplicable to circuits with dependent sources. To apply this theorem, we have to consider only the zero-state response by taking all the initial conditions to be zero. GATE ELECTRONICS 2020 https://t.me/GateElectronics

Assertion (A): A non-sinusoidal wave can be expressed in terms of sine waves of different frequencies which are multiples of the frequency of fundamental. Reason (R): If negative half of a complex wave is a reproduction of the positive half, the even harmonics are absent. A.Both A and R are correct and R is correct explanation of A B.Both A and R are correct but R is not correct explanation of A C.A is true, R is false D.A is false, R is true Answer: Option B

Can we use open loop OP-AMP in linear application. If not, why? Ans. When operating OP-AMP in open loop, the output is either negative or positive saturation or positive saturation or switches between positive and negative saturation levels. For this reason, open loop OP-AMP configurations are not used in liner applications.

What are characteristics of an ideal OP-AMP ? Ans. 1. Ad = ∞ R1 = ∞, so that almost any signal sources can drive it there is no loading of the preceding stage. R0 = 0 so that output can drive an infinite number of other devices. V0 = 0 when Vin = 0 BW = ∞, so that any frequency signal from 0 to ∞ Hz amplified without attenuation. CMRR = ∞ so that o/p common mode noise voltage is zero. SR = ∞, so that V0 changes simultaneously with input voltage changes.