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Q&A

General Q&A about the design and function of electronic systems, electric power systems and infrastructure, their theory, and tools specific to those fields. Read these guidelines before posting.

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28%
+0 −3
Current and voltage of inductor

How do I find the current through the inductor and the voltage of the inductor after the switch is closed?

2 answers  ·  posted 2y ago by MissMulan‭  ·  last activity 2y ago by MissMulan‭

66%
+2 −0
Select resistor for a diode

Suppose we have this circuit How do I pick a appropriate value for the resistor R1?

3 answers  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

66%
+2 −0
Diode like a frequency mixer

Based on this paper on Wiki a diode can be described as a frequency mixer due to the exponential relationship between current and voltage.What I don't get from which point to which point do we meas...

1 answer  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

75%
+4 −0
Thermal relief for through-hole on multi-layer PCB

When using through-hole ("THR") connectors on a multi-layer PCB, I frequently notice problems with the ground pins, when these are connected to the ground plane(s) through various "thermal relief" ...

1 answer  ·  posted 2y ago by Lundin‭  ·  edited 2y ago by Nick Alexeev‭

60%
+1 −0
SPI modes difference

What is a difference between SPI stream and memory mapped SPI? PS SPI is a peripheral.

2 answers  ·  posted 2y ago by FrankLEE‭  ·  last activity 2y ago by DavidCary‭

SPI
75%
+4 −0
What is the difference between emitter and collector of a transistor?

In all descriptions of how (non-FET) transistors work I've seen, there is an inherent symmetry: There's either an n-doped layer between two p-doped, or a p-doped between two n-doped, and the descri...

2 answers  ·  posted 2y ago by celtschk‭  ·  last activity 2y ago by Olin Lathrop‭

71%
+3 −0
Type II compensation network for a non-ideal transconductance amplifier

I am designing a DC/DC converter in the control loop of which a transconductance amplifier (OTA) is used. This part of circuit looks like this: To determine the needed characteristics, I am usin...

1 answer  ·  posted 2y ago by Mu3‭  ·  edited 2y ago by Mu3‭

66%
+2 −0
$Q$ and $\overline{Q}$ in bistable multivibrator

In this bistable multivibrator which is $Q$ and which is $\overline{Q}$?

1 answer  ·  posted 2y ago by MissMulan‭  ·  last activity 2y ago by Olin Lathrop‭

60%
+1 −0
A signal with one mode or with three or more modes

The term "Discrete" uses to describe a signal with two modes, but is there a term to describe a signal with just one mode or with three or more modes? Question update: Also, isn't a wave with just...

3 answers  ·  posted 2y ago by deleted user  ·  edited 2y ago by deleted user

50%
+0 −0
Tunnel current equation

The current through the tunnel diode is: where $I_{f}$ is the current from the Shockley diode equation and $I_{tunnel}$ is the tunnel current. Is there an expression for the tunnel current or i...

0 answers  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

66%
+4 −1
Motor Controller - What might be the purpose of these resistors?

I was looking at the video of the Tesla Model 3 motor controller(400VDC, 500A) disassembly and noticed a resistor network as in the picture below. They are 2k resistors(SMD code 202). See the pic...

4 answers  ·  posted 2y ago by 2kind‭  ·  last activity 2y ago by DSI‭

60%
+1 −0
Adding resistance to varactor circuit

If we a varactor and we want to control let's say the resonant frequency of the circuit ,in my schematic we must add R1 correct?Else we create a low resistance path for current to flow not through ...

2 answers  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

71%
+3 −0
3+3 doesn’t show 6

I have a problem which I don’t understand how to solve. I have this 2-bit adder, but when I select A1AO to be (11)2 3 and B1BO to be (11)2 3 and run it on Logisim it doesn’t show me 6. Instead it s...

2 answers  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

60%
+1 −0
Division of binary numbers logic circuit

If we want to divide two numbers I have problem implementing this logic.I am posting 1 images with 2 different steps to the solution. In example a) the most significant digits of the divident >...

2 answers  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

57%
+2 −1
2 bit subtractor using full subtractor

Can we make a n-bit subtractor using full subtractors or if we want do subtract one binary from another we must use full adders and use the complement of the 2nd number to do the subtraction? I ha...

1 answer  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

75%
+4 −0
What is this metal panel under power lines?

I was hiking around the Berkshires in western Massachusetts yesterday, and came across this metal panel where some power lines were crossing a ridge: The panel is a few meters wide, and appe...

1 answer  ·  posted 2y ago by Olin Lathrop‭  ·  last activity 2y ago by DSI‭

16%
+0 −8
HOW TO OPTIMIZE POWER USAGE FOR HOME [closed]

I HAVE A METER LIKE THIS BEHIND MY HOUSE MY NEIGBOR SLOWED IT DOWN SOMEHOW HE SAID HE OPENED IT UP AND DID SOMETHING TO IT NOW HE PAYS LOWER ELECTRICAL BILLS THAN ME BUT HE HAS COLLEGE DEGREE IN ...

0 answers  ·  posted 2y ago by ElectroRat‭  ·  edited 2y ago by Olin Lathrop‭

66%
+2 −0
Input offset voltage/bias current noise contribution in operational amplifiers

In noise analysis of operational amplifiers, the following is considered: Noise generated by the external components (resistors in feedback network etc.) Noise generated by the operational ampl...

1 answer  ·  posted 2y ago by Mu3‭  ·  last activity 2y ago by Olin Lathrop‭

25%
+0 −4
Electric circuit with antenna

Moderator's note: This is getting ridiculous. You keep posting these drawings that are barely legible. The scribbling is bad enough, but the uncropped images are unacceptable. The image you ori...

1 answer  ·  posted 2y ago by MissMulan‭  ·  last activity 2y ago by Olin Lathrop‭

50%
+0 −0
JFET equation of current

Is this equation valid only when a JFET in saturation mode , correct? because in the ohmic region the JFET acts like a voltage controlled resistor and increase in VDS increases the resistance of th...

0 answers  ·  posted 2y ago by MissMulan‭

28%
+0 −3
Is it safe to cover a floor lamp, with an Aluminum metal pie plate? [closed]

Please see the image below. I'm trying to convert my IKEA NYFORS floor lamp into a reading light, by covering the top with an Aluminium pie plate. Will this be a fire or electrical hazard? Does an...

0 answers  ·  posted 2y ago by TextKit‭  ·  closed 2y ago by Olin Lathrop‭

66%
+2 −0
Diodes used in mixers

Suppose we have this circuit which is supposed to be an unbalanced frequency mixer. But how does the diode generate a signal with new frequencies at the output?

2 answers  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

60%
+1 −0
Extract DC component of mixed signal

How can we extract a DC signal from a mixed signal?If we want to extract the AC component of a signal we can use a blocking capacitor to remove any DC offset but how do we achieve the opposite?Can ...

1 answer  ·  posted 2y ago by MissMulan‭  ·  last activity 2y ago by Andy aka‭

66%
+2 −0
MOSFET differential to single ended converter intuition

How does the differential to single ended converter work? In order for the circuit to work, Q1 and Q3 must be in the saturation region and depending on the voltage inputs, one of Q2 and Q4 will be...

1 answer  ·  posted 2y ago by MissMulan‭  ·  edited 2y ago by Peter Mortensen‭

33%
+0 −2
Voltage of tank circuit is invalid

In a previous question we found that for a critically damped oscillation: $$ I(t) = 2 t e^{-0.5 t} $$But if we integrate to find the voltage through the capacitor: $$ V_{CO} + \frac{1}{C} \cd...

1 answer  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

75%
+4 −0
Capacitor in 2nd stage of opamp

Inside a op-amp after the stage where the differential signal is converted to single ended , there is further amplification of the DC signal.For AC signals there is a capacitor parallel to the tran...

1 answer  ·  posted 2y ago by MissMulan‭  ·  last activity 8mo ago by Lorenzo Donati‭

42%
+1 −2
Critically damped oscillation issue

I have a question about this circuit:(critically damped oscillation) For a critically damped oscillation for a series RLC circuit the equation of current has this form I(t)=D1te^(-at)+D2e^(-at) ...

2 answers  ·  posted 2y ago by MissMulan‭  ·  edited 8mo ago by Lorenzo Donati‭

71%
+3 −0
Battery voltage: to boost or to connect in series.

Background. I have a legacy battery system that is comprised of twenty-four 12V Li-ion battery modules (self-protected), enclosed in a shell with the charging connection provided as a common groun...

1 answer  ·  posted 2y ago by DSI‭  ·  last activity 2y ago by Olin Lathrop‭

71%
+3 −0
Trouble understanding how to use adjustable LDO regulator

The question being asked Ultimately, I want to know why the output voltage wasn't the expected (via calculation) 11.72V when the estimated drop-out voltage at the ~0.1A load was about 200mV. The i...

2 answers  ·  posted 2y ago by cosined‭  ·  edited 8mo ago by Lorenzo Donati‭

62%
+3 −1
Help with differential to single ended voltage converter

Hello I don't understand how this differential to single-ended voltage converter can work. What I don't understand is why we place a current mirror(a current mirror copies the current flowing thr...

3 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 2y ago by Circuit fantasist‭

60%
+1 −0
Unexpected phase shift in results

I find the current flowing through the capacitor $$\begin{align} I_{C_1}(t)&=\dfrac{\mathrm{d}}{\mathrm{d}t}\left[V_1(t)-I_{C_1}(t)R_1\right] \\ {}&= \dfrac{\mathrm{d}}{\mathrm{d}t}\left...

2 answers  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by coquelicot‭

50%
+1 −1
Current and voltage in AC circuits without impedance

How can we find the equation of current and voltage of a capacitor circuit if the input voltage is AC without using the impedance formula Xc = -jωC?. We have for homework to find the equation of...

1 answer  ·  posted 3y ago by MissMulan‭  ·  last activity 3y ago by Olin Lathrop‭

71%
+3 −0
During a Li-ion cell charge or discharge at 1C rate, are the electrode interfaces at thermodynamic equilibrium?

Is the cell voltage (at a modest charging rate) mostly determined by thermodynamics on the electrode surfaces and resistances of electrolyte and electrode particles, or there is a non-negligible ki...

1 answer  ·  posted 3y ago by leventov‭  ·  last activity 3y ago by coquelicot‭

66%
+2 −0
Contactor control - Higher voltage PWM

I have a battery pack that consists of 18650 battery cells(14 cells in series max.). Hence, the voltage of the battery pack will be between 35V and 60V(to be on the safe side) I am designing a BMS...

2 answers  ·  posted 3y ago by 2kind‭  ·  edited 8mo ago by Lorenzo Donati‭

75%
+4 −0
Meaning of some components around voltage reference in SMPS

I have generated flyback convertor schematic by TI's Webench Power Designer. Parameters: universal AC input (85-265V AC) 5V, 2A output isolated UC3843A controller Basically I understand f...

2 answers  ·  posted 3y ago by Chupacabras‭  ·  last activity 3y ago by a concerned citizen‭

77%
+5 −0
Is there a way to reliably measure antenna return loss outside a lab?

Assume I'm a complete beginner at RF. Is there a way to measure return loss of an antenna, in such a manner that I can reliably reproduce the measurement later on? What I'm talking about is produ...

2 answers  ·  posted 3y ago by Lundin‭  ·  last activity 1y ago by TonyStewart‭

37%
+1 −3
What is the popular 12 V DC jack connector?

I'm designing a PCB for a project. 12 volt input power supply is provided externally, so the user will buy a power adapter, so putting a popular DC jack on the PCB is the best choice.

2 answers  ·  posted 3y ago by vigneshtnj‭  ·  last activity 2y ago by DavidCary‭

66%
+2 −0
What is the purpose of paralleling capacitors on the input/output of a power converter?

In the design of a power converter, picking the appropriate capacitors for the input and output of the converter is quite important. It is relatively easy to calculate the necessary values for a gi...

1 answer  ·  posted 3y ago by Mu3‭  ·  last activity 3y ago by Olin Lathrop‭

77%
+5 −0
Capacitor ESR vs. Impedance

One of the ceramic capacitors that I've found(link to the capacitor) specifies the following characteristics at 10 kHz: The difference in value is quite significant, almost 100 fold. Which grap...

3 answers  ·  posted 3y ago by 2kind‭  ·  last activity 3y ago by TonyStewart‭

30%
+1 −5
Is this AD8307 fake?

I am trying to test a AD8307. Here are my connections: (pins not shown are left unconnected, and also pin 8). I get a quiescent output voltage at pin 4 of about 850 mV with respect to ground, w...

1 answer  ·  posted 3y ago by coquelicot‭  ·  edited 3y ago by coquelicot‭

60%
+1 −0
Estimating the input capacitance of an BLDC motor controller

Problem Description I am trying to design a BLDC inverter and I am in doubt of what would be the right approach for estimating the input capacitor size/type. Doing it empirically or throwing every...

2 answers  ·  posted 3y ago by 2kind‭  ·  edited 8mo ago by Lorenzo Donati‭

71%
+3 −0
Why are antenna PCB traces square instead of rounded?

While doing some reading on RF designs I ran across this paragraph: I have never designed an RF circuit, but all the PCB trace antennas I have seen on development boards are square. For example,...

2 answers  ·  posted 3y ago by Kranulis‭  ·  last activity 3y ago by TonyStewart‭

75%
+4 −0
Design considerations for a synchronous DC/DC converter

In the field of DC/DC conversion, one can build a synchronous DC/DC converter (also referred to as synchronous rectification). This practice involves replacing a diode with a MOSFET switch. As far...

2 answers  ·  posted 3y ago by Mu3‭  ·  edited 8mo ago by Lorenzo Donati‭

71%
+3 −0
How could you model a 10M/100M Ethernet PHY architecture?

Application notes for microcontrollers or other ICs that have an internal 10M/100M ethernet PHY module differ in their requirements for the external interface components. It seems that the PHY des...

1 answer  ·  posted 3y ago by DavidE‭  ·  last activity 3y ago by Olin Lathrop‭

69%
+7 −2
Why is the resistance of water so high and still so dangerous?

Measuring the resistance of water from my tap I got 500kOhm. Adding considerable amount of salt brought it down to 20kOhm: The question I have is why water is such a danger for short circuits if t...

4 answers  ·  posted 3y ago by Kranulis‭  ·  edited 8mo ago by Lorenzo Donati‭

77%
+5 −0
Can you call an IC pin 'N.C' if it has hidden functionality?

The particular IC I ran into this issue with was DS3231 RTC. The pin configuration shows: However, the datasheet specifies To my knowledge, 'N.C' appears on ICs when it is decided to use a cer...

1 answer  ·  posted 3y ago by Kranulis‭  ·  last activity 3y ago by Olin Lathrop‭

IC
60%
+1 −0
Max V/Hz value for motor

I want to run a specific motor in the open loop. How to calculate the maximum ratio of V/f to run it? Am I looking at Ld or Lq value for this? Let's say these are the characteristics - haven't ch...

2 answers  ·  posted 3y ago by 2kind‭  ·  edited 8mo ago by Lorenzo Donati‭

55%
+3 −2
Who is familiar with PocketLink semiconductor and or Tesla Model 3 electronics

I got my hands on a Tesla Model 3 aftermarket module (Display/Cluster) The IC's are labled with the brand 'PocketLink' Id like to know more about what these parts are. Chip1: PocketLink B2 003...

0 answers  ·  posted 3y ago by Steven83‭  ·  edited 3y ago by Lundin‭

66%
+2 −0
Is there a tool or trick for bending TO220 leads

Small-shop question here. Is there a convenient tool for making the bend shown below, other than a pair of pliers that happens to be just the right size, and is it worth it for qty low 100's? ...

1 answer  ·  posted 3y ago by Pete W‭  ·  edited 3y ago by Lundin‭

60%
+1 −0
Why is it is always power consumption or power delivered more in usage?

In circuit analysis why always the power has upper hand over energy? Even if we consider a simple battery circuit with a bunch of resisitors we always use the terms power delivered,absorbed,consump...

3 answers  ·  posted 3y ago by aditya98‭  ·  last activity 3y ago by Andy aka‭