Question of the Week - Answer 250224https://learnemc.com/qotw-250224

EMC Question of the Week: February 24, 2025 Which radiated emissions specification is the most stringent at 100 MHz? FCC Part 15 Class B CISPR 32 Class B MIL-STD-461 RE102 CISPR 25 (automotive) Class 5 Answer The best answer is “c” although a good...

Question of the Week - Answer 200316https://learnemc.com/qotw-200316

EMC Question of the Week: March 16, 2020 The third harmonic of a continuous clock signal shows up as a narrow band peak in a conducted emissions measurement. How does the value measured with an average detector compare to the value measured with a peak...

Question of the Week - Answer 260112https://learnemc.com/qotw-260112

EMC Question of the Week: January 12, 2026 A noise source generates narrow impulses that appear at a constant repetition rate. For measurements in the frequency range from 30 to 1000 MHz with a 120-kHz resolution bandwidth, which of these repetition...

Question of the Week - Answer 210517https://learnemc.com/qotw-210517

EMC Question of the Week: May 17, 2021 The connection inductance of an 0603 SMT decoupling capacitor that is well-mounted to a printed circuit board 2 or 3 layers above the power/ground plane pair is typically a couple nanohenries hundred picohenries...

Question of the Week - Answer 221024https://learnemc.com/qotw-221024

EMC Question of the Week: October 24, 2022 The inductance of a tightly wound coil of wire with N turns is approximately proportional to N N2 wire radius coil radius Answer The best answer is “b.” The inductance of a coil of wire is approximately...

Question of the Week - Answer 201019https://learnemc.com/qotw-201019

EMC Question of the Week: October 19, 2020 When driving a CMOS load (capacitive termination), overshoot and ringing on an otherwise good digital waveform is a clear indication that the _______ has not been properly controlled. connection inductance...

Question of the Week - Answer 250324https://learnemc.com/qotw-250324

EMC Question of the Week: March 24, 2025 Which of these two-port networks is fully characterized by its S-parameters? (a) (b) (a) and (b) (a) and (b) and (c) Answer The best answer is “a.” If the S-parameters were determined by driving each of these...

Question of the Week - Answer 210524https://learnemc.com/qotw-210524

EMC Question of the Week: May 24, 2021 In order to function effectively, an EMC ground structure should be connected to the earth electrically small relatively big all of the above Answer The best answer is “c.” To take advantage of the EMC ground...

Question of the Week - Answer 210830https://learnemc.com/qotw-210830

EMC Question of the Week: August 30, 2021 A circuit board sends a signal down an unshielded twisted wire pair as illustrated in the figure. The differential-mode characteristic impedance of the wire pair is 100 Ω. The common-mode characteristic...

Question of the Week - Answer 220110https://learnemc.com/qotw-220110

EMC Question of the Week: January 10, 2022 At 10 MHz, the internal inductance of a #24 copper wire is more than 100 nH/m about 50 nH/m negligible undefined Answer The best answer is “c.” At MHz frequencies and higher, the internal inductance of a wire...

Question of the Week - Answer 200824https://learnemc.com/qotw-200824

EMC Question of the Week: August 24, 2020 In a multiwire transmission line, parallel signal conductors with the same impedance to ground carry currents I1 and I2, respectively, where I1 and I2 point in the same direction. The differential current on...

Question of the Week - Answer 260309https://learnemc.com/qotw-260309

EMC Question of the Week: March 9, 2026 A shielded cable connects to a circuit board mounted in a plastic enclosure. To minimize EM emissions and maximize EM immunity, the cable shield should generally connect to the circuit board ground planes...

Question of the Week - Answer 210712https://learnemc.com/qotw-210712

EMC Question of the Week: July 12, 2021 A ferrite toroid with signal wires wrapped in the direction indicated in the figure, serves as a common-mode choke a differential-mode choke an ideal transformer a DC block Answer The correct answer is “a.”...

Question of the Week - Answer 241223https://learnemc.com/qotw-241223

EMC Question of the Week: December 23, 2024 Which parameter of the connection between a decoupling capacitor and the power planes is most important to consider when attempting to optimize the high-frequency performance of the decoupling capacitor?...

Question of the Week - Answer 251027https://learnemc.com/qotw-251027

EMC Question of the Week: October 27, 2025 A differential signal propagates on a pair of microstrip traces then transitions to a twisted wire pair when it leaves the circuit board. Which of the following would cause a differential-mode to common-mode...

Question of the Week - Answer 240715https://learnemc.com/qotw-240715

EMC Question of the Week: July 15, 2024 A 2-meter coaxial cable is used to convey a single-ended 100-Mbps digital signal between two circuit boards in a system. The signal integrity is good, but there is a 10-ampere DC current flowing on the cable...

Question of the Week - Answer 240527https://learnemc.com/qotw-240527

EMC Question of the Week: May 27, 2024 A differential signal propagates on two loosely coupled, parallel microstrip traces. Each trace has a 50-Ω characteristic impedance to the ground plane and the differential-mode impedance is 100 Ω. If the traces...

Question of the Week - Answer 231106https://learnemc.com/qotw-231106

EMC Question of the Week: November 6, 2023 A 12-volt DC motor driver is laid out on a circuit board in a plastic enclosure that has a power input connector and a motor cable connector. To minimize EM emissions, the two connectors should be located over...

Question of the Week - Answer 240311https://learnemc.com/qotw-240311

EMC Question of the Week: March 11, 2024 A device-under-test consists of a 10-cm by 10-cm circuit board in a plastic enclosure with an attached power cord. A DC-to-DC converter on the board operating at 1 MHz is responsible for a radiated emissions...

Question of the Week - Answer 230828https://learnemc.com/qotw-230828

EMC Question of the Week: August 28, 2023 The circuit board ground layout shown in the figure is recommended for boards without a nearby chassis. This is a classic example of partitioning (zoning) decoupling a Faraday cage poor design advice Answer The...

Question of the Week - Answer 260105https://learnemc.com/qotw-260105

EMC Question of the Week: January 5, 2026 A switching power supply with a fixed duty cycle creates narrow impulses that appear at a repetition rate equal to the switching frequency. For measurements in the frequency range from 30 to 1000 MHz with a 120...

Question of the Week - Answer 251208https://learnemc.com/qotw-251208

EMC Question of the Week: December 8, 2025 The datasheet for a DC-to-DC power converter (12 V to 3.3 V) switching at 1 MHz recommends the layout shown in the figure. All components are on Layer 1. Layer 2 is a solid return (GND) plane. Which of the...

Question of the Week - Answer 221121https://learnemc.com/qotw-221121

EMC Question of the Week: November 21, 2022 The purpose of the capacitors in the figure is to provide low-pass filtering high-pass filtering power bus decoupling propagation delay Answer The best answer is “b.” These are DC-blocking capacitors on...

Question of the Week - Answer 210405https://learnemc.com/qotw-210405

EMC Question of the Week: April 5, 2021 Two 0603 MLCC capacitors are used to decouple a single power input of an IC. One of them has a nominal value of 0.10 μF. For the best high-frequency performance, the other one should have a value of 0.10 μF 10 μF...

Question of the Week - Answer 230522https://learnemc.com/qotw-230522

EMC Question of the Week: May 22, 2023 If a pulse-width-modulated signal has a fixed transition time, which duty cycle produces the most power at the switching frequency? 1% 10% 50% 90% Answer The best answer is “c.” The signal power at DC is...

Question of the Week - Answer 220328https://learnemc.com/qotw-220328

EMC Question of the Week: March 28, 2022 Which specification of an EMI test receiver is used to determine the noise floor? 1-dB gain compression Nominal Dynamic Range (NDR) Displayed Average Noise Level (DANL) Level Measurement Uncertainty (LMU) Answer...

Question of the Week - Answer 221205https://learnemc.com/qotw-221205

EMC Question of the Week: December 5, 2022 An LISN (or AMN) used for conducted emissions measurements always measures the voltage between a power input and a power input return circuit ground system ground the earth Answer The best answer is “c.” LISN...

Question of the Week - Answer 260216https://learnemc.com/qotw-260216

EMC Question of the Week: February 16, 2026 In a conducted emissions test setup, the DUT is 40 cm from a vertical metal plane. Changing the separation distance from 40 cm to 20 cm, we would expect the value of the parasitic capacitance to the plane...

Question of the Week - Answer 201026https://learnemc.com/qotw-201026

EMC Question of the Week: October 26, 2020 Which of the following transient protection components is a "crowbar" device (so called, because it acts like a short circuit when the voltage across its terminals exceeds the threshold)? TVS diode varistor...

Question of the Week - Answer 240610https://learnemc.com/qotw-240610

EMC Question of the Week: June 10, 2024 For a differential trace pair, terminating each trace in the odd-mode impedance provides a matched termination for both the odd-mode and even-mode propagation provided the coupling between the traces is strong...

Question of the Week - Answer 210705https://learnemc.com/qotw-210705

EMC Question of the Week: July 5, 2021 The crosstalk between two matched 50-Ω stripline traces plotted as a function of frequency has a maximum value of -30 dB. If the distance between the traces is increased, reducing the mutual capacitance between...

Question of the Week - Answer 210816https://learnemc.com/qotw-210816

EMC Question of the Week: August 16, 2021 Testing an EUT on a 30-meter open-field site, an EMI test receiver measures a 29 dB(μV/m) peak at 100 MHz. With the DUT powered off, the measured signal amplitude is 26 dB(μV/m). What is the likely amplitude of...

Question of the Week - Answer 230116https://learnemc.com/qotw-230116

EMC Question of the Week: January 16, 2023 If a circuit board has single-ended analog circuits operating at 100 MHz and single-ended digital circuits operating at 100 Mbps, the return currents should almost always be routed on the same plane(s) the...

Question of the Week - Answer 250526https://learnemc.com/qotw-250526

EMC Question of the Week: May 26, 2025 A 1-Mbps digital signal is transmitted across a circuit board, through a connector, and on to a shielded wiring harness. An RC low pass filter is used to limit the bandwidth of the transmitted signal. Which filter...

Question of the Week - Answer 210201https://learnemc.com/qotw-210201

EMC Question of the Week: February 1, 2021 When deciding whether it is necessary to use a matched termination on a digital signal trace, it's important to compare the propagation delay to the signal's bit rate transition time clock period jitter Answer...

Question of the Week - Answer 221107https://learnemc.com/qotw-221107

EMC Question of the Week: November 7, 2022 The EMC test set-up in the photo is designed for measuring CISPR 32 radiated emissions CISPR 12 radiated emissions electrostatic discharge immunity radiated immunity Answer The best answer is “d.” The first...

Question of the Week - Answer 220530https://learnemc.com/qotw-220530

EMC Question of the Week: May 30, 2022 For a rectangular metal enclosure whose length is greater than its width, and whose width is greater than its height, the lowest resonant frequency is a function of its length only length and width only length,...

Question of the Week - Answer 230717https://learnemc.com/qotw-230717

EMC Question of the Week: July 17, 2023 A clock driver sends a 10-Mbps clock signal to 4 devices spread out on a 10-cm x 10-cm printed circuit board. Each device has a 5-pF input capacitance, and the signals are routed on microstrip traces. What...

Question of the Week - Answer 250127https://learnemc.com/qotw-250127

EMC Question of the Week: January 27, 2025 A 5-Ω digital signal source drives a 10-nF load through a lossless, 1-m cable with a propagation delay of 5.6 ns. The characteristic impedance of the cable is 50 Ω. What is the transition time of the received...

Question of the Week - Answer 220221https://learnemc.com/qotw-220221

EMC Question of the Week: February 21, 2022 The "rabbit ears" antenna shown in this figure is a dipole antenna two monopole antennas a horn antenna a phased array Answer The correct answer is “a.” The two extendable "rabbit ears" are the two elements...

Question of the Week - Answer 230227https://learnemc.com/qotw-230227

EMC Question of the Week: February 27, 2023 To reduce circuit board conducted and radiated emissions due to switching noise, choose DC-to-DC converters that have the smallest possible switching frequency footprint quiescent current output current...

Question of the Week - Answer 231002https://learnemc.com/qotw-231002

EMC Question of the Week: October 2, 2023 A GNSS signal (1.6 GHz) is conveyed from an antenna to a circuit board on a coaxial cable. On the circuit board, the center conductor of the cable is connected to the receiver via a 5-cm trace. The coaxial...

Question of the Week - Answer 220725https://learnemc.com/qotw-220725

EMC Question of the Week: July 25, 2022 A high-speed digital signal source on a circuit board produces the pseudo-differential outputs SIG+ and SIG-. When SIG+ is 3.3 V (relative to the ground plane), SIG- is 0V. When SIG+ is 0 V, SIG- is 3.3V. If SIG+...

Question of the Week - Answer 230508https://learnemc.com/qotw-230508

EMC Question of the Week: May 8, 2023 A common-mode current probe measures 10 μA of current at 50 MHz on a shielded twisted pair cable. The twisted wire pair itself carries 30 μA of common-mode current at 50 MHz. How much 50-MHz current flows on the...

Question of the Week - Answer 251110https://learnemc.com/qotw-251110

EMC Question of the Week: November 10, 2025 A digital clock source (5 Mbps, 2 Ω) provides a signal to three devices on the same printed circuit board. Each of the three device inputs is a 5-pF capacitance and is connected to the source with a 10-cm...

Question of the Week - Answer 230710https://learnemc.com/qotw-230710

EMC Question of the Week: July 10, 2023 Which type of induced transient in an EMC compliance test generally has the greatest time-rate-of-change in voltage (i.e., the highest dV/dt)? ESD EFT damped sinusoid lightning Answer The best answer is “a.” An...

Question of the Week - Answer 200413https://learnemc.com/qotw-200413

EMC Question of the Week: April 13, 2020 An unmatched CMOS digital input can usually be modeled, to a first order, as a resistance of 50 to 100 Ω a resistance of 5 to 10 kΩ an inductance of 5 to 10 nH a capacitance of 5 to 10 pF Answer The correct...

Question of the Week - Answer 200713https://learnemc.com/qotw-200713

EMC Question of the Week: July 13, 2020 The best layer stack-up for a 6-layer printed circuit board is, S-S-P-G-S-S S-G-S-S-P-S SP-G-S-S-G-S none of the above Answer The best answer is "d". The truth is there is no guideline for the optimum layer...

Question of the Week - Answer 200518https://learnemc.com/qotw-200518

EMC Question of the Week: May 18, 2020 To send a 1 Mbps CMOS digital signal a distance of 20 cm on a ribbon cable, it's important to use a matched termination use Manchester encoding control the transition time use a ferrite on the cable Answer The...

Question of the Week - Answer 201207https://learnemc.com/qotw-201207

EMC Question of the Week: December 7, 2020 Generally, the best way to send a high-speed differential signal, V+ and V-, on an unshielded three-wire ribbon cable is to use the two outer wires one inner and one outer wire V+ on inner and V- on both outer...