Hardware Engineering Interview Questions

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Here are 10 basic interview questions for hardware engineering roles.

What is the difference between passive and active components?

Active electronic components require an external power source and actively control or amplify signals (e.g., transistors, op-amps). Passive electronic components do not need power and interact with signals by storing, filtering, or dissipating energy (e.g., resistors, capacitors, inductors).

What is RMS Voltage?

RMS voltage represents the DC voltage that dissipates the same amount of power as the average power dissipated by the AC voltage. i.e. the voltage of a sinusoidal signal that provides the same power to a load as a DC equivalent circuit.
E.g. Our domestic mains supply is 230V. This means that the AC current we are receiving from the mains produces the same power as a DC signal of 230V.

What are the functions of a transistor?

Switching and Amplification

What is the use of a motor driver? Give examples of motor driver ICs.

When a motor is interfaced to a microcontroller board, we require a motor driver because the current provided by the pins of most microcontrollers is not sufficient to run a DC motor. The motor driver IC steps up the current from microcontroller and provides the required power to run the DC motor. A motor driver IC controls the speed and direction of the motor.
We can directly connect the motor to the pins of our microcontroller and run it using PWM if sufficient current is provided but this is not recommended. This can damage the board in the long run. The back EMF of the motor can cause voltage spikes at microcontroller pins.

Examples of motor driver ICs:

• LM293D
• ULN20003

What is PWM?

PWM stands for pulse width modulation. The pulse width is altered such that narrow width provides low voltage and wider pulse provides higher voltage. Basically it is a digital signal that behaves like an analog signal and can be used to control analog actuators.

What is the difference between BJT and MOSFET?

Explain the difference between TTL and CMOS families.

TTL uses bipolar transistors and has higher power consumption, faster switching speeds, and better noise immunity. TTL is faster but consumes more power.

CMOS uses complementary pairs of metal-oxide-semiconductor transistors and has lower power consumption, slower switching speeds, and greater susceptibility to noise. CMOS logic is slower but consumes less power.

What are the ideal characteristics of op-amp?

Ideal op-amp characteristics include infinite open-loop gain, infinite input impedance, zero output impedance, and infinite bandwidth.

How does negative feedback improve op-amp performance?

Negative feedback is crucial to stabilize and improve op-amp performance. It reduces distortion, minimizes output offset voltage, and narrows the input-output differential, making op-amps suitable for various applications.

Why do we use a bypass capacitor?

A bypass capacitor, also known as a decoupling capacitor or smoothing capacitor, is a capacitor connected in parallel with an electronic component, typically an integrated circuit (IC) or an active component like a transistor. Its primary purpose is to improve the stability and performance of electronic circuits by addressing issues related to power supply noise and voltage fluctuations.