Question of the Week - Answer 221128https://learnemc.com/qotw-221128

EMC Question of the Week: November 28, 2022 When a circuit board layout has a "quiet I/O ground" under the connector, that ground should usually be connected to other grounds on the board through resistors through ferrites at a single point none of the...

Question of the Week - Answer 231016https://learnemc.com/qotw-231016

EMC Question of the Week: October 16, 2023 The figure below shows four DC-to-DC step-up converter layouts. In each case, the traces shown are on the top layer, and the layer below is a solid ground plane. If the input voltage comes from a source off...

Question of the Week - Answer 250428https://learnemc.com/qotw-250428

EMC Question of the Week: April 28, 2025 Conduction current in copper is characterized by the flow of electrons electric field perpendicular to the surface time-rate-of-change of the electric field cross product of electric and magnetic fields Answer...

Question of the Week - Answer 230213https://learnemc.com/qotw-230213

EMC Question of the Week: February 13, 2023 An LED mounted in the wall of a plastic enclosure is connected to a circuit board through a 30-cm unshielded twisted wire pair. The LED driver produces a single-ended, 3.3-V, 50-MHz, PWM signal. The radiated...

Question of the Week - Answer 251124https://learnemc.com/qotw-251124

EMC Question of the Week: November 24, 2025 Which signal has the strongest harmonic at 425 MHz if they both have the same amplitude and a 50% duty cycle? 5 MHz clock with a 1 ns transition time 25 MHz clock with a 3 ns transition time either of the...

Question of the Week - Answer 231225https://learnemc.com/qotw-231225

EMC Question of the Week: December 25, 2023 Which of the following EMC design guidelines for circuit board layouts, widely published online, has been debunked in peer-reviewed publications? 20H rule avoid 90o trace bends put guard rails on clock traces...

Question of the Week - Answer 240624https://learnemc.com/qotw-240624

EMC Question of the Week: June 24, 2024 Which of these has the largest capacitance to earth? rod antenna in a radiated emissions setup laptop computer 5 cm above ground automobile 20 cm above ground commercial aircraft 10 km above ground Answer The...

Question of the Week - Answer 220523https://learnemc.com/qotw-220523

EMC Question of the Week: May 23, 2022 A microprocessor in a BGA package with 300 connections is mounted on the top side of a 24-layer circuit board. Layer 2 is a solid ground plane. 3.3-volt power to the processor and other components is distributed...

Question of the Week - Answer 250804https://learnemc.com/qotw-250804

EMC Question of the Week: August 4, 2025 Which of the following curves in the datasheet of a common-mode choke is the most helpful for predicting the performance of the choke in an actual product? attenuation vs. frequency impedance magnitude vs....

Question of the Week - Answer 250929https://learnemc.com/qotw-250929

EMC Question of the Week: September 29, 2025 A good rule of thumb for ensuring that the crosstalk between microstrip traces is -20 dB or lower is to maintain a spacing between the traces that is at least three times the trace width length height...

Question of the Week - Answer 241125https://learnemc.com/qotw-241125

EMC Question of the Week: November 25, 2024 In the water circuit analogy to electric circuits, the quantity analogous to the velocity of signal propagation in a transmission line is the velocity of the water molecules water molecule vibrations sound in...

Question of the Week - Answer 231009https://learnemc.com/qotw-231009

EMC Question of the Week: October 9, 2023 The figure below shows four DC-to-DC step-down converter layouts. In each case, the traces shown are on the top layer, and the layer below is a solid ground plane. Which of these layouts is best for containing...

Question of the Week - Answer 240325https://learnemc.com/qotw-240325

EMC Question of the Week: March 25, 2024 An ESD generator has an energy-storage capacitor, Cs, a distributed capacitance, Cd, a discharge resistor, Rd, and a ground strap. Which component is primarily responsible for producing the initial current spike...

Question of the Week - Answer 210308https://learnemc.com/qotw-210308

EMC Question of the Week: March 8, 2021 When a bulk current injection (BCI) test is performed on a wire harness, which induced-noise quantity is approximately the same on every wire in the harness? voltage current power all of the above Answer The best...

Question of the Week - Answer 250630https://learnemc.com/qotw-250630

EMC Question of the Week: June 30, 2025 For a signal propagating in a parallel-wire transmission line, which of the following must remain constant in order to avoid reflections? the ratio of the voltage to the current the ratio of the electric- to...

Question of the Week - Answer 240122https://learnemc.com/qotw-240122

EMC Question of the Week: January 22, 2024 If a 200-MHz square wave with a peak-to-peak amplitude of 1.0 volt is input to a spectrum analyzer, the measured amplitude of the first harmonic should be 1.0 volt (120 dBμV) 0.71 volts (117 dBμV) 0.63 volts...

Question of the Week - Answer 201130https://learnemc.com/qotw-201130

EMC Question of the Week: November 30, 2020 Measured ESR of a 47-nF X7R MLCC as described in CVEL-17-069 Above 30 MHz, the loss in a multi-layer ceramic decoupling capacitor is primarily due to conductor loss dielectric loss radiation loss eddy...

Question of the Week - Answer 251103https://learnemc.com/qotw-251103

EMC Question of the Week: November 3, 2025 A 100-MHz signal generator in a shielded enclosure drives a matched load on a circuit board through a 50-cm coaxial cable. On the board, the signal travels 8 cm on either a pair of coplanar traces or a...

Question of the Week - Answer 220627https://learnemc.com/qotw-220627

EMC Question of the Week: June 27, 2022 A 25 MHz clock signal and a 125 MHz clock signal both have 0.8 ns transition times. They have the same amplitude, the same 50% duty cycle, and drive the same load. Which signal has more power in the harmonic at...

Question of the Week - Answer 230410https://learnemc.com/qotw-230410

EMC Question of the Week: April 10, 2023 When a single-ended signal drives a wire with no return conductor, the worst-case radiated emissions are well over the limit. Adding a current-return wire and a matched termination would reduce the worst-case...

Question of the Week - Answer 220103https://learnemc.com/qotw-220103

EMC Question of the Week: January 3, 2022 At 1 MHz, which electrical quantity is difficult to measure because it's not well-defined? voltage between two points on a copper plane current density on the surface of a copper plane signal voltage on a...

Question of the Week - Answer 240617https://learnemc.com/qotw-240617

EMC Question of the Week: June 17, 2024 An IC drives a circuit board trace connected to pin 2 with a 20-MHz clock signal. The 100-MHz component of the current driven onto the trace is 1 mA. The 100-MHz current returning to the IC through one or more of...

Question of the Week - Answer 231030https://learnemc.com/qotw-231030

EMC Question of the Week: October 30, 2023 A differential signal is routed on a pair of traces 0.25 mm over a ground plane for a distance of 5 cm. The pair continues for another 5 cm beyond the edge of the ground plane. At the point where the ground...

Question of the Week - Answer 240729https://learnemc.com/qotw-240729

EMC Question of the Week: July 29, 2024 Two modules communicate with each other at 100 Mbps over a 2-meter coaxial cable. Common-mode current on the cable causes the system to fail radiated emissions at 300 MHz. One possible solution is to filter the...

Question of the Week - Answer 241007https://learnemc.com/qotw-241007

EMC Question of the Week: October 7, 2024 A connection between a coaxial cable and a microstrip trace on a circuit board is made through two parallel connector blades. The two blades are identical with a length of 2 cm. They are separated by an air...

Question of the Week - Answer 221219https://learnemc.com/qotw-221219

EMC Question of the Week: December 19, 2022 If a 100-MHz sine wave and a 100-MHz square wave both have the same peak-to-peak amplitude, which has the stronger harmonic at 100 MHz as measured on an EMI test receiver? the sine wave the square wave they...

Question of the Week - Answer 200803https://learnemc.com/qotw-200803

EMC Question of the Week: August 3, 2020 Two parallel circuit board traces located 1 mm above a ground plane have a mutual capacitance of 20 pF/m. If their height above the ground plane is reduced to 0.25 mm, their mutual capacitance will decrease...

Question of the Week - Answer 231023https://learnemc.com/qotw-231023

EMC Question of the Week: October 23, 2023 Two high-speed signals are routed parallel to each other on identical microstrip traces. The self-inductance of each trace is 6 nH/cm and the mutual inductance between them is 0.6 nH/cm. If both traces have...

Question of the Week - Answer 220321https://learnemc.com/qotw-220321

EMC Question of the Week: March 21, 2022 In an ISO 11452-4 bulk current injection test, what percentage of the harness current returns on the metal tabletop? virtually all of it it depends on the DUT it depends on the DUT and supporting equipment...

Question of the Week - Answer 210215https://learnemc.com/qotw-210215

EMC Question of the Week: February 15, 2021 An ESD simulator (R = 330 Ω, C = 150 pF) discharges into a load with a resistance, RL. Which of the following load resistances receives the most energy from the simulator? RL = 100 Ω RL = 330 Ω RL = 1000 Ω...

Question of the Week - Answer 240129https://learnemc.com/qotw-240129

EMC Question of the Week: January 29, 2024 A wire carrying DC current runs too close to a compass and affects the reading. A shield is wrapped around the wire and connected to the frame ground at the source end. Which of the following shield material...

Question of the Week - Answer 240422https://learnemc.com/qotw-240422

EMC Question of the Week: April 22, 2024 A 100-Mbps signal carried on a coaxial cable is received by an IC on a 15-cm-long, 2-layer circuit board. Four possible designs for the receiver are shown in the figure. Option (a) uses a single-ended signal...

Question of the Week - Answer 240205https://learnemc.com/qotw-240205

EMC Question of the Week: February 5, 2024 To evaluate the worst-case high-frequency coupling between two long microstrip traces routed side by side on a circuit board, it's best to use a 2D static electric-field solver 2D static magnetic-field solver...

Question of the Week - Answer 201005https://learnemc.com/qotw-201005

EMC Question of the Week: October 5, 2020 At low frequencies, the internal inductance of a round copper wire is proportional to the wire diameter proportional to the wire radius proportional to the loop area about 50 nH/m Answer The best answer is "d"....

Question of the Week - Answer 240415https://learnemc.com/qotw-240415

EMC Question of the Week: April 15, 2024 Increasing the twist-rate of a certain twisted wire pair from 1.5 twists/cm to 2.0 twists/cm is found to increase the inductance per unit length by 3%. Based on this result, we expect the capacitance per unit...

Question of the Week - Answer 241209https://learnemc.com/qotw-241209

EMC Question of the Week: December 9, 2024 A 50-Ω source drives a 10-pF load capacitance through a 20-cm circuit board trace. The controlled-impedance trace has a 50-Ω characteristic impedance and a per-unit-length capacitance of 1.1 pF/cm. If the...

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 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...