GATE 1987 ECE Analog Circuits (Analog Electronics) - Video Solutions

1. In the figure, if the CMRR of the operational amplifier is 60 dB, then the magnitude of the output voltage is

Answer: 100 mV

Solution : https://www.youtube.com/watch?v=ESpNuIMnYZo


2. The configuration of cascode amplifier is
a. CE – CE
b. CE – CB
c. CC – CB
d. CC – CC

Answer: B

Solution : https://www.youtube.com/watch?v=rjgvNommuXU


3. In case of class A amplifiers, the ratio of efficiency of transformer coupled amplifier to efficiency of a transformer less amplifier is
a. 2.0
b. 1.36
c. 1.0
d. 0.5

Answer: A

Solution : https://www.youtube.com/watch?v=A-lOzfa17B8
 

GATE 1987 Video Solutions on Digital Circuits

1. The subtraction of a binary number Y from another binary number X, done by adding 2’s compliment of Y to X, results in a binary number without overflow. This implies that the result is
a. Negative and is in normal form
b. Negative an is in 2’s compliment form
c. Positive and is in normal form
d. Positive and is in 2’s compliment form

Answer: B

Solution : https://www.youtube.com/watch?v=SMBnnJJrDDE


2. Choose the correct statements relating to the circuit of figure shown

Answer:B & D

Solution : https://www.youtube.com/watch?v=zryK-Yl3-Dg


3. A ripple counter using negative edge triggered D flip-flops is shown below. The flip-flops are cleared to ‘0’ at the R input. The feedback logic is to be designed to obtain the count sequence shown in the same figure. The correct feedback logic is :

Answer:A

Solution : https://www.youtube.com/watch?v=qljzFR3B6TM


4. Fill in the blanks of the statements below concerning the following logic families :
Standard TTL (74XXLL)
Low Power TTL (74LXX)
Low Power Schottky TTL (74LSXX)
Schottky TTL (74SXX)
Emitter Coupled Logic (ECL)
CMOS logic
a. Among the TTL families, …………. Family requires considerably less power than the standard TTL and also has comparable propagation delay.
b. Only the …………… family can operate over a wide range of power supply voltages.

Answer: (a) Low Power Schottky , (b) CMOS

Solution : https://www.youtube.com/watch?v=jPrNVnV0ZCA


5. For a logic family, given that
V_OH is the minimum output high level voltage.
V_OL is the maximum output low level voltage.
V_IH is the minimum acceptable input low level voltage.
V_IL is the maximum acceptable input low level voltage.
Then the correct relationship is
a. V_IH>V_OH>V_IL>V_OL
b. V_OH > V_IH > V_IL > V_OL
c. V_IH > V_OH > V_OL > V_IL
d. V_OH > V_IH > V_OL > V_IL

Answer:B

Solution : https://www.youtube.com/watch?v=nQ473i9xpF8

GATE 1987 Video Solutions on EDC (Electronic Devices and Circuits)

1.       Consider two energy levels : E₁, E eV above the Fermi level and E₂, E eV below the Fermi level. P₁ and P₂ are the probabilities of E₁ and E₂ being occupied by the electron respectively. Then

a.       P₁ > P₂

b.      P₁ = P₂

c.       P₁ < P₂

d.      P₁ and P₂ depend on number of free electrons

Answer:C

Solution :  https://www.youtube.com/watch?v=XrZAi2Q0S7Q

2.       In an intrinsic semiconductor, the free electron concentration depends on

a.       Effective  mass of electrons only

b.      Effective mass of holes only

c.       Temperature of the semiconductor

d.      Width of the forbidden energy band of the semiconductor

Answer:C

               Solution :  https://www.youtube.com/watch?v=C61o_nRoaBc

3.       According to the Einstein relation, for any semiconductor, the ratio of diffusion constant to mobility of carriers

a.       Depends upon the temperature of the semiconductor

b.      Depends upon the type of the semiconductor

c.       Varies with life time of the semiconductor

d.      Is a universal constant

Answer:A

               Solution :  https://www.youtube.com/watch?v=CNsSUnfw85Q

4.       Direct band gap semiconductors

a.       Exhibit short carrier lifetime and they are used for fabricating BJTs

b.      Exhibit long carrier lifetime and they are used for fabricating BJTs

c.       Exhibit short carrier lifetime and they are used for fabricating LASERs

d.      Exhibit long carrier lifetime and they are used for fabricating LASERs

Answer:C

               Solution :  https://www.youtube.com/watch?v=fzNBPuE9hEE

5.       The diffusion capacitance of a PN junction

a.       Decreases with increasing current and increasing temperature

b.      Decreases with decreasing current and increasing temperature

c.       Increases with increasing current and increasing temperature

d.      Does not depend on current and temperature

Answer:B

               Solution :  https://www.youtube.com/watch?v=YgQjfNh4JiU

6.       The pinch off voltage for an n-channel JFET is 4 volts, then pinch off occurs for V_DS when V_GS = -1 volts is

a.       3 volts

b.      5 volts

c.       4 volts

d.      1 volts

Answer:A

               Solution : https://www.youtube.com/watch?v=6dIMNQ-GqKM