BEE Bachelor of Electrical Engineering Analog and Digital Electronics Questions and Answers

Question 1

An ideal operational amplifier (op-amp) is configured as a non-inverting amplifier. Which of the following characteristics is NOT representative of this ideal model?

Accepted Answer

Zero common-mode rejection ratio (CMRR)

Answer

An ideal op-amp is characterized by infinite open-loop gain, infinite input impedance, and zero output impedance. It also has an infinite Common-Mode Rejection Ratio (CMRR), meaning it perfectly rejects any voltage common to both inputs. Therefore, a zero CMRR is not a characteristic of an ideal op-amp; in fact, it represents the worst-case scenario where common-mode signals are amplified as much as differential signals.

Question 2

A digital designer needs to simplify the Boolean expression Y = (A + B)'. According to De Morgan's theorems, which of the following expressions is equivalent?

Accepted Answer

Y = A' . B'

Answer

De Morgan's second theorem states that the complement of a sum (OR operation) is equal to the product (AND operation) of the complements. Therefore, the expression (A + B)' is equivalent to A' . B'.

Question 3

In a BJT common-emitter amplifier configuration, what is the typical phase relationship between the input signal at the base and the output signal at the collector?

Accepted Answer

The output is 180 degrees out of phase with the input.

Answer

The common-emitter amplifier is an inverting amplifier. This means that as the input voltage at the base increases, the collector current increases, causing a larger voltage drop across the collector resistor. This results in a decrease in the collector voltage. Consequently, the output signal at the collector is 180 degrees out of phase with the input signal at the base.

Question 4

A technician is troubleshooting a Class B push-pull amplifier and observes distortion on the output waveform precisely at the zero-crossing point. What is the most likely cause of this issue?

Accepted Answer

Crossover distortion

Answer

Crossover distortion occurs in Class B amplifiers because there is a small region around the zero-crossing point where both transistors are turned off. This happens because the input signal must overcome the base-emitter voltage (around 0.7V for silicon transistors) before a transistor starts to conduct. This 'deadband' causes a flat spot on the output waveform as it crosses zero.

Question 5

Which type of Analog-to-Digital Converter (ADC) operates by sequentially testing each bit from the most significant bit (MSB) to the least significant bit (LSB) to find the digital equivalent of an analog signal?

Accepted Answer

Successive-Approximation ADC

Answer

A Successive-Approximation Register (SAR) ADC works by using a binary search algorithm. It starts by setting the MSB to 1 and compares the resulting analog voltage (from an internal DAC) to the input signal. Based on the comparison, the bit is either kept or cleared, and the process repeats for the next bit until the LSB is determined. This method allows for a good balance between speed and resolution.

BEE - Bachelor of Electrical Engineering Practice Test

BEE - Bachelor of Electrical Engineering Practice Test

BEE Bachelor of Electrical Engineering Analog and Digital Electronics Questions and Answers