Electronics & Communication Engineering Mock Interview Questions & Practice

Explain the difference between the three configurations of a BJT amplifier (CE, CB, CC).

Key points to cover:

• CE: moderate impedance, high gain, 180° phase shift
• CB: low input / high output impedance, no phase shift, used at high frequency
• CC (emitter follower): high input / low output impedance, near-unity gain, used for buffering

Explain De Morgan's theorems and their significance in digital logic.

Key points to cover:

• (A AND B)' = A' OR B', and (A OR B)' = A' AND B'
• Allows converting between AND/OR/NOT forms
• Useful for implementing logic with only NAND or only NOR gates

What is the purpose of a voltage follower (unity gain buffer) circuit using an op-amp?

Key points to cover:

• Provides high input impedance and low output impedance
• Gain of 1
• Isolates/buffers a signal source from a load

What is the difference between energy signals and power signals?

Key points to cover:

• Energy signal has finite total energy and zero average power
• Power signal has finite, nonzero average power and infinite energy
• Notes energy signals are typically time-limited, power signals periodic/persistent

What is the region of convergence (ROC) in the context of the Laplace transform, and why does it matter?

Key points to cover:

• The set of values of s for which the transform integral converges
• The same transform expression can correspond to different time-domain signals
• Depending on the ROC, so it must always accompany the transform

What is the difference between a system's transient response and its steady-state response?

Key points to cover:

• Transient response is the temporary behavior right after a change in input
• Before settling
• Steady-state response is the behavior after transients have died out

What is the difference between double sideband (DSB) and single sideband (SSB) AM?

Key points to cover:

• DSB transmits both upper and lower sidebands (and typically the carrier)
• SSB transmits only one sideband
• Reduces bandwidth and transmit power at the cost of more complex demodulation

What is the purpose of error detection and correction codes in digital communication?

Key points to cover:

• Detect (and in some schemes correct) errors introduced by noise/interference
• During transmission
• Improves reliability without always needing to retransmit

What is multipath fading in wireless communication, and what causes it?

Key points to cover:

• Variations in received signal strength
• Caused by a signal reaching the receiver via multiple paths
• Interfering constructively or destructively

What is the difference between near-field and far-field regions around an antenna?

Key points to cover:

• Near-field: close region where field structure doesn't behave like a simple wave
• Far-field: far enough that the wave behaves as a simple radiating wave
• Far-field has a predictable inverse-distance amplitude falloff

What causes reflections on a transmission line, and how is the reflection coefficient defined?

Key points to cover:

• Occurs when the line's characteristic impedance doesn't match the load
• Reflection coefficient: ratio of reflected wave's amplitude to incident wave's
• Determined by the impedance mismatch

What is antenna radiation pattern, and what information does it convey?

Key points to cover:

• A graphical representation of an antenna's radiated power/field strength
• As a function of direction
• Conveys where the antenna radiates most/least strongly, lobe structure

What is the difference between the design abstraction levels: behavioral, RTL, gate-level, and layout?

Key points to cover:

• Behavioral describes what the circuit does functionally
• RTL describes data flow between registers and the logic operating on it
• Gate-level describes interconnected logic gates, layout describes physical geometry

What is the difference between RISC and CISC processor architectures?

Key points to cover:

• RISC uses a small set of simple, fixed-length instructions
• Roughly one cycle each
• CISC uses a larger set of complex, variable-length instructions

What is the difference between a hard real-time system and a soft real-time system?

Key points to cover:

• Hard real-time: missing a deadline is a system failure
• E.g. airbag deployment timing
• Soft real-time: missing a deadline degrades quality but is not catastrophic