Introduction: Top Question Bank
Although there are some question banks available online for hardware engineer wrote and interview tests, some of the questions are outdated and have not been updated, and some of the answers are incorrect, which can be misleading for new engineers. Therefore, this question bank was created.
This question bank selects the majority of the question banks available online for hardware engineer written and interview tests, some of which were provided by netizens. Most of the question banks provide reference answers for recent graduates and engineers looking to change jobs to practice and learn. The question bank has been carefully selected to provide valuable written and interview test questions for everyone to reference.
If you have any good question banks, you can also leave a message or send a private message to provide them, and we can compile them together for the convenience of hardware engineers to practice with.
Body: Top Question Bank
1. Please explain the working principle of the Watchdog.
The Watchdog has two important signals: clock input and reset output. During operation, the CPU sends a clock signal to the Watchdog, also known as “feeding the dog.” If the system fails, the CPU cannot send continuous clock signals, and the Watchdog outputs a reset signal to the CPU, resetting the system.
2. Please list three typical ESD models.
The three typical ESD models are Human Body Model (HBM), Machine Model (MM), and Charged Device Model (CDM).
3. Which six hazardous substances are restricted by the RoHS directive in electronic and electrical equipment?
The RoHS directive restricts the use of six hazardous substances, including lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBBs), and polybrominated diphenyl ethers (PBDEs).
4. The basic transistor amplifier circuits have three types of connections: common emitter, common collector, and common base. Please briefly describe the characteristics of these three basic amplifier circuits.
Common emitter: The common emitter amplifier circuit has the effect of amplifying both current and voltage. Its input impedance is moderate, the output impedance is relatively high, and the frequency band is narrow. It is suitable for general amplification.
Common collector: The common collector amplifier circuit only has the function of current amplification. Its input impedance is high, the output impedance is low, and it has the characteristic of voltage following. It is often used as the input and output stages of multi-stage amplifiers.
Common base: The common base circuit only has the function of voltage amplification. Its input impedance is small, the output impedance and voltage amplification ratio are equivalent to those of the common emitter circuit. It has good high-frequency characteristics and is suitable for wide-band amplification circuits.
5. What are the different ways of interstage coupling in multi-stage amplifiers? Which coupling method has the most severe DC offset? Which coupling method can achieve impedance matching?
There are three coupling methods: direct coupling, RC coupling, and transformer coupling. The direct coupling has the most severe DC offset, while transformer coupling can achieve impedance matching.
6. Define the following terms: coupling, decoupling, bypass, and filtering.
Coupling: the interconnection between two originally separate circuits or two separate parts of a circuit that allows energy to be transferred from one circuit or part to another.
Decoupling: the prevention of energy from one circuit being exchanged or fed back to another circuit, to avoid unpredictable feedback that could affect the normal operation of the next amplifier stage or circuit.
Bypass: the process of filtering out high-frequency components of a signal mixed with low-frequency signals by using electronic components, usually capacitors, allowing only the low-frequency signal to enter the next stage without the high-frequency signal.
Filtering: the process of filtering out specific frequency bands in a signal to suppress and prevent interference, which is an important measure to ensure signal quality.
7. What are the competition and glitches?
In logic circuits, competition occurs when the input signals to a gate have different delays and arrive at the gate at different times. Glitches are momentary errors in the output caused by competition.
8. What is the difference between passive filters and active filters?
Passive filters are composed of passive components such as resistors, capacitors, and inductors. They are designed to provide a low-impedance path for harmonic currents at a specific frequency and can be classified as either tuning filters or high-pass filters. Passive filters are simple, cost-effective, and reliable, making them a widely used passive harmonic mitigation solution.
Active filters, on the other hand, are composed of active components such as operational amplifiers and resistors/capacitors. They do not use inductors, are smaller and lighter, and can amplify and buffer the filtered signal. Active filters are actually amplifiers with a specific frequency response. However, their bandwidth is limited by the amplifier’s open-loop voltage gain and input impedance, which restricts their operating frequency range.
9. What are the components of a phase-locked loop (PLL)?
A phase-locked loop (PLL) consists of three main components: a phase detector, a loop filter, and a voltage-controlled oscillator (VCO). The phase detector compares the phase of the input signal with that of a reference signal and produces an error signal that is filtered by the loop filter. The filtered error signal is then used to adjust the frequency of the VCO so that its output frequency tracks that of the input signal.
10. What are the voltage ranges for logic 0 and logic 1 in the RS-232C standard?
The RS-232C electrical standard uses negative logic, where the voltage range for logic 0 is between +5V to +15V, and the voltage range for logic 1 is between -5V to -15V. The voltage range between -5V and +5V is considered unstable or undefined.
11. What is the difference between UART, USRT, and USART?
UART stands for Universal Asynchronous Receiver/Transmitter, which is a device used for asynchronous communication between two devices.
USRT stands for Universal Synchronous Receiver/Transmitter, which is a device used for synchronous communication between two devices.
USART stands for Universal Synchronous/Asynchronous Receiver/Transmitter, which is a device that can handle both synchronous and asynchronous communication between two devices.
12. What are the four parts that make up the character frame format of asynchronous serial communication?
The character frame format of asynchronous serial communication consists of four parts: start bit, data bits, parity bit, and stop bit.
13. Please list some differential balanced signal interfaces that you know.
RS422, RS485, RJ45, CAN, USB, LVDS.
14. What are the three elements of electromagnetic interference?
The three elements of electromagnetic interference are the electromagnetic interference source, the interference propagation path, and the interference-sensitive equipment.
15. Please explain what crosstalk and ringing are.
Crosstalk refers to the interference of one signal by another signal, and the principle of its action is electromagnetic field coupling. Capacitive coupling causes coupling current, while inductive coupling causes coupling voltage.
Ringing is caused by the impedance mismatch of the signal line itself, which causes signal reflection and superposition, resulting in oscillating waveforms.
16. What signals have you encountered that require controlling a single-ended impedance of 50 ohms and 75 ohms? What signals have you encountered that require controlling the impedance?
Generally, high-frequency signal lines are 50 ohms to 60 ohms. 75 ohms is mainly used for video signal lines. The differential impedance of USB signal lines is 90 ohms, and the differential impedance of Ethernet differential signal lines is 100 ohms. The differential impedance of RS422, RS485, and CAN differential signals is 120 ohms.