Operational Amplifiers

Question 1

How is an Op-Amp coupled ?

Answer 1

DC coupled

Question 2

What is direct coupling or conductive coupling or DC coupling ?

Answer 2

Transfer or electrical energy

Question 3

How is electrical energy transfered in DC coupling ?

Answer 3

Via physical contact through a conducting medium

Question 4

What are the other methods of coupling electrical cicuits ?

Answer 4

Inductive and Capacitive circuits

Question 5

How is the low frequency response of direct coupling ?

Answer 5

Very good.

Question 6

How good is the low frequency response of direct coupling ?

Answer 6

It passes the full spectrum along with DC (0 Hz)

Question 7

Why is DC coupling used as default in IC Op Amps ?

Answer 7

Difficult to fabricate large coupling capacitors on chip

Question 8

What is the gain of an Op Amp like ?

Answer 8

High gain

Question 9

What kind of electronic amplifier is an Op Amp (V or I) ?

Answer 9

Voltage

Question 10

Why is it that the characteristics of an Op Amp are dependent on the external components and not on temperature coefficients and the manufacturing process ?

Answer 10

Negative feedback

Question 11

What are some examples of differential amplifier (apart from Op-Amp) ?

Answer 11

Fully Differential Amplifier
Instrumentation Amplifier
Isolation Amplifier
Negative Feedback Amplifer

Question 12

What is a fully differential amplifier ?

Answer 12

Like an op amp, with 2 outputs

Question 13

What is an instrumentation amplifier ?

Answer 13

Uses 3 op amps

Question 14

What is an isolation amplifier ?

Answer 14

Similar to an instrumentation amplifier, but with greater tolerance to common mode voltages

Question 15

What is negative feedback amplifier ?

Answer 15

Built from one or more op amps, + resistive feedback network

Question 16

How is open loop gain measured ?

Answer 16

In the absence of feedback network from output to input

Question 17

How is gain measured, in general ?

Answer 17

Output / Input voltage

Question 18

What is the open loop gain of an ideal op amp ?

Answer 18

Infinite

Question 19

What is the input impedance of an ideal op amp ?

Answer 19

Infinite input impedance

Question 20

What is a consequence of infinite input impedance ?

Answer 20

Zero input current

Question 21

What is the bandwidth of an ideal op amp ?

Answer 21

Infinite

Question 22

What is the phase shift of an ideal op amp ?

Answer 22

Zero phase shift

Question 23

What is phase shift ?

Answer 23

Phase difference in between two or more quantities (waves)

Question 24

What is the slew rate of an ideal op amp ?

Answer 24

Infinite

Question 25

What is slew rate ?

Answer 25

Maximum rate of change of output voltage per unit time

Question 26

What is the CMRR of an ideal op amp ?

Answer 26

Infinite

Question 27

What is the PSRR of an ideal op amp ?

Answer 27

Infinite

Question 28

Why are closed loop amplifiers prefered over open loop amplifiers ?

Answer 28

Open loop gain is not well controlled by the manufacturing process

Question 29

What is a voltage follower ?

Answer 29

A buffer. (Gain of 1)

Question 30

What are filters ?

Answer 30

Remove unwanted signals during signal processing

Question 31

What kind of filters do op amps find application in ?

Answer 31

Active filters

Question 32

Why are active filters called active ?

Answer 32

They contain active components like amplifiers or FETs

Question 33

What is the disadvantage of a passive filter ?

Answer 33

Amplitude of the output is always less than the input

Question 34

How do the active components in an active filter amplify the output signal ?

Answer 34

By drawing energy from an external source

Question 35

What is a low pass or high cut filter ?

Answer 35

Passes signals with frequency lower than cutoff

Question 36

What is a high pass or low cut filter ?

Answer 36

Passes signals with frequency higher than cutoff

Question 37

What is a band pass filter ?

Answer 37

Passes frequencies in a range and rejects outside the range

Question 38

When are isolation amplifiers used ?

Answer 38

Applications where electrical insulation in between source and output is desired

Question 39

What is an application of an isolation amplifier ?

Answer 39

Medical instrumentation Source - Sensor Target - Patient

Question 40

What is the order of a filter ?

Answer 40

Number of RC poles used in the filter