Question of the Week - Answer 211108https://learnemc.com/qotw-211108

EMC Question of the Week: November 8, 2021 It is usually ok for circuit board traces to cross over a gap in the ground plane as long as the signals they carry, are pseudo-differential rarely switch (e.g. RESET or ENABLE) either of the above none of the...

Question of the Week - Answer 240108https://learnemc.com/qotw-240108

EMC Question of the Week: January 8, 2024 If applying a spread spectrum to a digital clock reduces peak emissions at the clock frequency by 9 dB, we would expect the quasi-peak emissions to be reduced by 0 dB 6 dB 9 dB more than 9 dB Answer The best...

Question of the Week - Answer 240219https://learnemc.com/qotw-240219

EMC Question of the Week: February 19, 2024 On a cable with three wires: power, power-return, and ground, the common-mode current is the vector sum of the currents flowing on power and power-return power-return and ground all three wires either (a) or...

Question of the Week - Answer 200921https://learnemc.com/qotw-200921

EMC Question of the Week: September 21, 2020 The input signal of a two-port linear network is sinusoidal with an rms amplitude of 1 volt and a frequency of 100 MHz. What MUST be true about the output signal? The amplitude must be 1 volt or less. It...

Question of the Week - Answer 240902https://learnemc.com/qotw-240902

EMC Question of the Week: September 2, 2024 On a dry day, a person can experience an electrostatic discharge when reaching out to grasp a metal doorknob in a wooden door because the doorknob has a resistance to the earth capacitance to the earth...

Question of the Week - Answer 180604https://learnemc.com/qotw-180604

EMC Question of the Week: June 4, 2018 Which statement is generally true about the "equivalent series inductance" values published in the datasheets of SMT ceramic capacitors? They are more important than the nominal capacitance values. They...

Question of the Week - Answer 191111https://learnemc.com/qotw-191111

EMC Question of the Week: November 11, 2019 The most important parameter affecting the inductance of a ground strap is its length width thickness permeability Answer The best answer is "a". Of course, inductance is a property of current loops; and the...

Question of the Week - Answer 260601https://learnemc.com/qotw-260601

EMC Question of the Week: June 1, 2026 The figure plots the amplitude of the harmonics for a 1-Vpp 10-MHz trapezoidal waveform with 0.5-ns and 5-ns transition times. With a 5-ns transition time, there is a clear (sin x)/x shape with nulls at multiples...

Question of the Week - Answer 240708https://learnemc.com/qotw-240708

EMC Question of the Week: July 8, 2024 When a component on a multilayer board has two types of ground pins (e.g., analog and digital, or digital and power) they should all be connected to the same solid ground plane(s) unless the datasheet says...

Question of the Week - Answer 200330https://learnemc.com/qotw-200330

EMC Question of the Week: March 30, 2020 The input impedance of a long spool of cable (say 100 meters) measured at 500 MHz is approximately equal to the total resistance of the conductors termination impedance intrinsic impedance of the dielectric...

Question of the Week - Answer 250505https://learnemc.com/qotw-250505

EMC Question of the Week: May 5, 2025 If a multi-layer printed circuit board has a solid ground plane on Layer 2, then a ground fill on Layer 1 is usually not recommended. This is because filling empty areas of Layer 1 with ground often increases the...

Question of the Week - Answer 230403https://learnemc.com/qotw-230403

EMC Question of the Week: April 3, 2023 Generally, on a well-designed 10 x10 cm circuit board with power and ground planes separated by 0.25 mm or less, all of the decoupling capacitors connected to the planes are local global unnecessary 0.01 μF...

Question of the Week - Answer 230724https://learnemc.com/qotw-230724

EMC Question of the Week: July 24, 2023 A microstrip trace connects a 5-pF CMOS input pin to an external connector pin. Which layout generally provides the best ESD protection for the IC? TVS diode near the IC input pin TVS diodes near both IC and...

Question of the Week - Answer 200608https://learnemc.com/qotw-200608

EMC Question of the Week: June 8, 2020 For the DC/DC buck converter shown in the figure, the high-frequency switching current loop is the trace and pads connecting the converter IC to Cin Cout L GND Answer The correct answer is "a". The high-frequency...

Question of the Week - Answer 241118https://learnemc.com/qotw-241118

EMC Question of the Week: November 18, 2024 An active device is mounted on a 4-layer board with a GND plane on Layer 2 and a VCC plane on Layer 3. The spacing between Layers 2 and 3 is 1 mm. Which of the four decoupling capacitors depicted in the...

Question of the Week - Answer 250728https://learnemc.com/qotw-250728

EMC Question of the Week: July 28, 2025 A signal measured on a digital oscilloscope is sampled in the time-domain and displayed in the frequency domain. The resolution bandwidth in the frequency domain is primarily determined by the acquisition time...

Question of the Week - Answer 220117https://learnemc.com/qotw-220117

EMC Question of the Week: January 17, 2022 The signal received by an antenna passes through an amplifier that increases its voltage by 20 dB, it then experiences 3 dB of power loss as it travels through a cable connected to the input of an EMI test...

Question of the Week - Answer 220606https://learnemc.com/qotw-220606

EMC Question of the Week: June 6, 2022 The graph in this figure plots impedance as a function of distance from electric and magnetic dipole sources. Plots similar to this appear in countless EMC texts and articles. What type of impedance is this?...

Question of the Week - Answer 231113https://learnemc.com/qotw-231113

EMC Question of the Week: November 13, 2023 In an equipment rack, each piece of equipment should usually be grounded at a single point in the rack the front of the rack the back of the rack the front and back of the rack Answer The best answer is “d.”...

Question of the Week - Answer 201109https://learnemc.com/qotw-201109

EMC Question of the Week: November 9, 2020 Assuming the dielectric materials are the same, which transmission line would have the longest propagation delay? microstrip trace pair stripline trace pair unshielded parallel wires shielded twisted wire pair...

Question of the Week - Answer 220815https://learnemc.com/qotw-220815

EMC Question of the Week: August 15, 2022 To determine the characteristic impedance of a 1-km length of cable, use a high-frequency RLC meter to measure the input resistance inductance capacitance both (b) and (c) Answer The best answer is “a.” When a...

Question of the Week - Answer 230109https://learnemc.com/qotw-230109

EMC Question of the Week: January 9, 2023 Slowing the transition time of a 10 MHz trapezoidal waveform from 1 ns to 5 ns reduces the maximum amplitude of harmonics above 320 MHz by 0 dB 5 dB 7 dB 14 dB Answer The best answer is “d.” Harmonics fall off...

Question of the Week - Answer 230731https://learnemc.com/qotw-230731

EMC Question of the Week: July 31, 2023 Two planes in a circuit board form a patch antenna producing radiated emissions at 1.5 GHz. The circuit board sits on a 1-meter wooden table, and the emissions are measured in a semi-anechoic chamber at a 1-meter...

Question of the Week - Answer 180618https://learnemc.com/qotw-180618

EMC Question of the Week: June 18, 2018 The resistance per unit length of a balanced twisted-wire-pair transmission line is equal to the resistance per unit length of each wire twice the resistance per unit length of each wire half the resistance per...

Question of the Week - Answer 230306https://learnemc.com/qotw-230306

EMC Question of the Week: March 6, 2023 A voltage source drives a quarter-wave monopole that resonates at 300 MHz. The radiation resistance is 36 Ω. If a ferrite core (R = 80 Ω at 300 MHz) is placed on the monopole, the radiated emissions from the...

Question of the Week - Answer 221114https://learnemc.com/qotw-221114

EMC Question of the Week: November 14, 2022 Suppose the separation distance between two microstrip traces is increased, reducing the mutual capacitance between them by a factor of two. In this case, the mutual inductance between the two circuits will...

Question of the Week - Answer 221031https://learnemc.com/qotw-221031

EMC Question of the Week: October 31, 2022 The current distribution on a half-ounce copper plane below a microstrip trace at 100 MHz is mostly concentrated under the trace as indicated in the figure. At 1 GHz, we would expect the current distribution...

Question of the Week - Answer 250818https://learnemc.com/qotw-250818

EMC Question of the Week: August 18, 2025 Which of the following phrases best describes a requirement for an EMC ground? conductor of relatively large extent small relative to a wavelength return current path connection to the earth Answer The best...

Question of the Week - Answer 200525https://learnemc.com/qotw-200525

EMC Question of the Week: May 25, 2020 A ribbon cable is used to convey a single-ended 1-Mbps 3.3-volt digital signal between two circuit boards. A good estimate for the worst-case emissions around 100 MHz (as measured in an FCC Class B radiated...

Question of the Week - Answer 201228https://learnemc.com/qotw-201228

EMC Question of the Week: December 28, 2020 The amplitude of the 5th harmonic of a 3.3-volt, 10-MHz clock signal with a 1-ns transition time is approximately 600 mV 300 mV 30 mV 60 μV Answer The correct answer is “b.” There are several ways to quickly...

Question of the Week - Answer 220516https://learnemc.com/qotw-220516

EMC Question of the Week: May 16, 2022 A coaxial cable carrying a 100 Mbps digital signal connects a system controller in a metal box to a sensor board in a plastic box. To minimize the common-mode current on the cable shield, it's important to have a...

Question of the Week - Answer 190902https://learnemc.com/qotw-190902

EMC Question of the Week: September 2, 2019 A person charged to 15,000 volts catches an uncharged glass sphere as it falls through the air. The amount of charge transferred to the glass sphere depends on the sphere's resistance capacitance inductance...

Question of the Week - Answer 180212https://learnemc.com/qotw-180212

EMC Question of the Week: February 12, 2018 Some of the power in a differential-mode signal propagating down a transmission line is converted to common-mode when, the transmission line is not balanced there is a change in the electrical balance of the...

Question of the Week - Answer 221226https://learnemc.com/qotw-221226

EMC Question of the Week: December 26, 2022 Generally, a ferrite bead on a circuit board should never be in series with a signal trace an I/O trace a power trace a ground trace Answer The best answer is “d.” Traces labeled "ground" are usually...

Question of the Week - Answer 170703https://learnemc.com/qotw-170703

EMC Question of the Week: July 3, 2017 Ultimately, the current that flows out of an integrated circuit pin and on to a circuit board trace has to find its way to, whatever is connected to the other end of the trace the signal ground the product's earth...

Question of the Week - Answer 190415https://learnemc.com/qotw-190415

EMC Question of the Week: April 15, 2019 The Schelkunoff Decomposition breaks the overall shielding effectiveness value into three components: Reflection Loss (R), Absorption Loss (A) and a multiple reflections correction term (M). The Absorption Loss...

Question of the Week - Answer 250901https://learnemc.com/qotw-250901

EMC Question of the Week: September 1, 2025 Which of these currents is primarily responsible for radiated emissions from cables? odd mode even mode differential mode common mode Answer The best answer is “d.” It is the common-mode current on cables...

Question of the Week - Answer 240401https://learnemc.com/qotw-240401

EMC Question of the Day: April 1, 2024 Faraday cages were first developed in what century? 9th 19th 20th 21st Answer The correct answer is “a.” In 891, Alfred the Great, King of Wessex, had a problem. Waves of Danish invaders kept his armies busy far...

Question of the Week - Answer 201116https://learnemc.com/qotw-201116

EMC Question of the Week: November 16, 2020 A 100-Mbps single-ended signal propagates from its source to the edge of a circuit board on a microstrip trace. At the board edge, it transitions to a ribbon cable where the signal current flows on one wire...

Question of the Week - Answer 181001https://learnemc.com/qotw-181001

EMC Question of the Week: October 1, 2018 For a digital clock signal that resembles a 3.3 Vpp square wave, the amplitude of the first harmonic is approximately 2 volts is less than 0.2 volts may be more than 20 volts depends on the frequency of the...

Question of the Week - Answer 220228https://learnemc.com/qotw-220228

EMC Question of the Week: February 28, 2022 For the standard electrical outlets shown in the figure, the terminals that electrically connect to the earth outside the building are labeled HOT NEUTRAL GROUND Both NEUTRAL and GROUND Answer The best answer...

Question of the Week - Answer 221212https://learnemc.com/qotw-221212

EMC Question of the Week: December 12, 2022 Conducted emissions testing of a 12-volt device reveals that the noise on the power wire (VBATT+) is 12 dB over the limit. The noise on the power return wire (VBATT-) is 12 dB below the limit. This product...

Question of the Week - Answer 260511https://learnemc.com/qotw-260511

EMC Question of the Week: May 11, 2026 Differential signal trace pairs on the outer layer of a printed circuit board 0.25 mm or less over a solid copper plane should generally be tightly coupled be length matched have coplanar ground all of the above...

Question of the Week - Answer 211227https://learnemc.com/qotw-211227

EMC Question of the Week: December 27, 2021 In the digital oscilloscope display shown in the figure, what is the frequency of the second peak in the FFT? 1 kHz 2 kHz 3 kHz 4 kHz Answer The correct answer is “c.” The time-domain waveform (blue trace) is...

Question of the Week - Answer 240429https://learnemc.com/qotw-240429

EMC Question of the Week: April 29, 2024 A stripline trace in a circuit board is 0.2 mm wide and 0.25 mm from the planes above and below it. The dielectric is FR-4 (εr = 4.3). What is the ratio of the electric field strength to the magnetic field...

Question of the Week - Answer 220307https://learnemc.com/qotw-220307

EMC Question of the Week: March 7, 2022 The duty cycle of a PWM waveform increases from 50% to 90%. The amplitude, frequency and transition times stay the same. In the frequency domain, what happens to the amplitude of the first harmonic? increases...

Question of the Week - Answer 220131https://learnemc.com/qotw-220131

EMC Question of the Week: January 31, 2022 The quasi-peak amplitude in a radiated emissions measurement is 46 dB(μV/m). The quasi-peak limit at that frequency is 40 dB(μV/m). The measured value is over the limit by 6 dB(μV/m) 12 dB(μV/m) 20 dB(μV/m) 40...

Question of the Week - Answer 260323https://learnemc.com/qotw-260323

EMC Question of the Week: March 23, 2026 A metal sphere the size of a basketball (diameter = 24 cm) has an absolute capacitance of 13 pF. A metal sphere the size of a tennis ball (diameter = 6.7 cm) has an absolute capacitance of 3.7 pF. If they were...

Question of the Week - Answer 201214https://learnemc.com/qotw-201214

EMC Question of the Week: December 14, 2020 Reducing the video bandwidth on an EMI test receiver or spectrum analyzer impacts the measurement in a manner similar to reducing the resolution bandwidth reducing the signal bandwidth adding an attenuator to...

Question of the Week - Answer 250113https://learnemc.com/qotw-250113

EMC Question of the Week: January 13, 2025 Driven with the same ideal voltage source, between 10 MHz and 10 GHz, which of these antennas produces the highest radiated emissions at its resonant frequency? 20-cm matched 377-Ω parallel wires (2-cm...