(SEM V) THEORY EXAMINATION 2018-19 INTEGRATED CIRCUITS

INTEGRATED CIRCUITS (REC-501)

B.Tech (SEM-V) – AKTU
                                                                                                       Time: 3 Hours  Total Marks: 70

SECTION A

(Attempt all questions – 7 × 2 = 14 marks)

Q1 (a) What is full power bandwidth?

Full power bandwidth is the maximum frequency at which an operational amplifier can deliver its maximum output voltage swing without distortion. It is limited by the slew rate of the op-amp.

Q1 (b) What do you mean by slew rate?

Slew rate is the maximum rate of change of output voltage of an op-amp per unit time. It is expressed in V/µs and limits the high-frequency performance of the amplifier.

Q1 (c) Define input offset voltage.

Input offset voltage is the small differential DC voltage required between the input terminals of an op-amp to make the output voltage exactly zero.

Q1 (d) What is CMRR?

Common Mode Rejection Ratio (CMRR) is the ratio of differential gain to common-mode gain of an op-amp. It indicates the ability of the op-amp to reject common-mode signals.

Q1 (e) Define PSRR.

Power Supply Rejection Ratio (PSRR) is the ability of an op-amp to suppress variations in output voltage caused by fluctuations in power supply voltage.

Q1 (f) What is virtual ground?

Virtual ground is a point in an op-amp circuit that is at zero potential but not physically connected to ground. It occurs due to high gain and negative feedback.

Q1 (g) What is a current mirror?

A current mirror is a circuit that copies a reference current to one or more output branches, maintaining constant current regardless of load variations.

SECTION B

(Attempt any three – 3 × 7 = 21 marks)

Q2 (a) Explain the internal block diagram of IC 741 operational amplifier.

IC 741 consists of three main stages:

Input differential amplifier – provides high input impedance and high CMRR

Intermediate gain stage – provides high voltage gain

Output stage – provides low output impedance and drives load

Additional circuits include offset nulling, biasing, and compensation to ensure stability and proper operation.

Q2 (b) Explain the ideal and practical characteristics of an operational amplifier.

An ideal op-amp has infinite gain, infinite input impedance, zero output impedance, infinite bandwidth, and zero offset voltage.
A practical op-amp has finite gain, limited bandwidth, small offset voltage, finite slew rate, and non-zero output impedance.

Q2 (c) Explain inverting and non-inverting amplifier configurations.

In an inverting amplifier, the output is 180° out of phase with input and gain is −Rf/Rin.
In a non-inverting amplifier, output is in phase with input and gain is 1 + Rf/R1.
Both configurations are widely used in signal amplification.

Q2 (d) Explain the working of differential amplifier with neat diagram.

A differential amplifier amplifies the difference between two input signals while rejecting common-mode signals. It improves noise immunity and forms the input stage of most op-amps.

SECTION C

(Attempt any one – 1 × 7 = 7 marks)

Q3 (a) (i) How is short circuit protection achieved in the output stage of IC 741 op-amp?

(ii) Draw and explain the frequency response of IC 741.**

(i) Short circuit protection:
IC 741 uses current-limiting transistors in the output stage. When output current exceeds a safe value, these transistors limit the current, protecting the op-amp from damage due to short circuits.

(ii) Frequency response:
The frequency response of IC 741 shows high gain at low frequencies. Gain decreases at −20 dB/decade beyond the dominant pole frequency. The unity gain bandwidth is approximately 1 MHz.

OR

Q3 (b) What do you understand by base current mirror? How does it provide improvement over simple current mirror? Explain with neat circuit diagram.

A base current mirror includes additional circuitry to reduce error caused by base currents of transistors.
Compared to a simple current mirror, it provides improved accuracy and better current matching by compensating base current losses, thus enhancing performance.