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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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66%
+2 −0
Complementary transistor pairs - what is the point ?

I understand that some applications require NPN-PNP pairs with identical electrical characteristics. But I would like to understand why.

2 answers  ·  posted 3y ago by coquelicot‭  ·  edited 9mo ago by Lorenzo Donati‭

71%
+3 −0
Is there an easy way to measure the characteristic impedance of a cable using basic lab instruments?

As the title says, I'm interested in a simple technique to measure the characteristic impedance of a cable using only the instruments available in a school lab or to a (somewhat advanced) hobbyist....

1 answer  ·  posted 10mo ago by Lorenzo Donati‭  ·  edited 9mo ago by Lorenzo Donati‭

77%
+5 −0
Substituting multiple lower voltage resistors for a high voltage resistor

Certain high voltage resistors are fairly hard to get, such as the HVR37 series from Vishay. I'm looking at redesigning a board that produces 1000V via a transformer, but I want to use parts that ...

1 answer  ·  posted 3y ago by TimH‭  ·  edited 9mo ago by Lorenzo Donati‭

28%
+0 −3
Thermal stability coefficient [closed]

The thermal stability coefficient is defined to be: $S = \frac{dI_{C}}{dI_{CBO}}$ where $I_{CBO}$ is the reverse current of the BJT when voltage isnt applied to the base of the BJT. In case of a ...

0 answers  ·  posted 1y ago by MissMulan‭  ·  closed 9mo ago by Nick Alexeev‭

60%
+1 −0
Are a JFET's Idss and Vgs(off) values correlated?

I know that many JFETs parameters have a very large manufacturing spread, in particular, $I_{DSS}$ and $V_{GS(off)}$, as one can see (for example) in this datasheet excerpt: ... My question i...

1 answer  ·  posted 10mo ago by Lorenzo Donati‭  ·  edited 9mo ago by Nick Alexeev‭

77%
+5 −0
What effect will extreme temperatures have on characteristic impedance of a wire?

My scenario is this: radio equipment controlling an overhead crane inside a steel mill. Specifically it is used for transporting melting pots. With the current, unfortunate installation, the antenn...

2 answers  ·  posted 2y ago by Lundin‭  ·  last activity 9mo ago by Lorenzo Donati‭

77%
+5 −0
Low-pass filter after the output DAC in CD players

[Disclaimer. This is not for an academic class. I'm self-studying.] I’m reading an introductory book on DSP for audio and computer music [Steiglitz 1996, ISBN 0-8053-1684-1 p. 287]. One of the ...

4 answers  ·  posted 1y ago by Nick Alexeev‭  ·  last activity 9mo ago by Lorenzo Donati‭

77%
+5 −0
Possible stray current corrosion in reinforced concrete

I have a question about stray current corrosion in reinforced concrete. I am working on a project in a parking garage with PV-panels on top of the roof. The ground is directly connected to reinforc...

1 answer  ·  posted 1y ago by Willem ‭  ·  edited 9mo ago by Lorenzo Donati‭

50%
+0 −0
Pulse disappear in digital scope just by looking at different signal in other channel.

I have a HANTEK 6022BE oscilloscope and I'm monitoring three signals with it: FS (Frame sync clock). Pulse. Transfer complete. I'm using two channels of the scope to monitor a pair of these...

1 answer  ·  posted 1y ago by mohammadsdtmnd‭  ·  last activity 9mo ago by Lorenzo Donati‭

80%
+6 −0
DC offset correction loop (DC servo loop). What's its advantage, compared to a high-pass RC filter?

Once in a while in literature I see a DC offset subtraction loop. Here are a few more examples. DC servo loop removes a DC offset after an op-amp. DC servo loop removes DC current from a photo...

2 answers  ·  posted 12mo ago by misk94555‭  ·  edited 9mo ago by misk94555‭

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 9mo ago by Lorenzo Donati‭

66%
+2 −0
Is the noise of op-amps and ADCs Gaussian, possibly with zero mean?

I understand that white noise is not always Gaussian. In general, is the $V_{pp}$ and $V_{RMS}$ noise stated in operational amplifier and ADC datasheets Gaussian? And is its mean zero? Any exemptio...

1 answer  ·  posted 9mo ago by Joel‭  ·  last activity 9mo ago by Lorenzo Donati‭

83%
+8 −0
Is ESD overhyped?

I have seen many engineers talk about ESD protection but I had never seen its effects myself. I made many small DIY projects and I have used bare hands to touch ICs and their pins,but nothing got d...

10 answers  ·  posted 3y ago by aditya98‭  ·  last activity 9mo ago by rdtsc‭

66%
+6 −2
Titanic submarine control considerations

The submarine built by OceanGate went missing on 18th June 2023. A lot of online criticism was directed towards the control hardware of the submarine - Logitech F710 controller. However, why i...

3 answers  ·  posted 10mo ago by Elleanor Lopez‭  ·  last activity 9mo ago by Pogo‭

75%
+4 −0
Is concentric twist a common practice?

I have seen multiple sources on the web discussing what they call concentric twist harnesses. It boils down to having a wiring harness built in layers, where each layer is twisted around the previo...

0 answers  ·  posted 10mo ago by Sclrx‭

84%
+9 −0
Flyback transformer with Intrinsic Safety

I have no experience designing for Intrinsic Safety (IS), but need to do that now. I have read thru IEC 60079-11, which seems to be the relevant standard for my purposes. The board I need to desi...

4 answers  ·  posted 2y ago by Olin Lathrop‭  ·  last activity 10mo ago by Lorenzo Donati‭

77%
+5 −0
How to perform initialization of static storage variables in embedded systems?

Whenever declaring a variable in C outside a function at file scope or when specifying it as static, it gets assigned a life time known as static storage duration. Meaning it will be accessible thr...

1 answer  ·  posted 1y ago by Lundin‭  ·  last activity 10mo ago by Lorenzo Donati‭

71%
+3 −0
Choosing between common-drain JFET amplifier, and common-source

Do common-source JFET amplifiers have an advantage over common-drain? The JFET would be in a low noise photodiode amplifier. The signal is 100us pulses with 10us raise times. Here are the schema...

1 answer  ·  posted 10mo ago by misk94555‭  ·  last activity 10mo ago by Olin Lathrop‭

77%
+5 −0
What material is used in the tabs of power packages? (TO-220, D2PAK, etc.)

What material is used in the tabs of power packages? (TO-220, D2PAK, etc.) I would assume probably a tin-plated copper alloy, but I can't find a reference. Datasheets don't seem to mention the mat...

1 answer  ·  posted 10mo ago by Jason S‭  ·  last activity 10mo ago by Lorenzo Donati‭

66%
+2 −0
High power LC circuit with programmable resonant frequency

I intend to build a high-power series LC resonant circuit for the purpose of generating strong magnetic fields at a wide range of frequencies, mostly audio range (1-5000 Hz). The inductor coil is a...

1 answer  ·  posted 10mo ago by dcsuka‭  ·  edited 10mo ago by dcsuka‭

60%
+1 −0
How to convert dv/dt of noise into frequency for filter capacitor selection?

Noise can be coupled between signal lines through parasitic capacitance formed between these signal lines, as $i = C\frac{dv}{dt}$ where C is the capacitance between the signal lines. Another wa...

1 answer  ·  posted 10mo ago by Elleanor Lopez‭  ·  last activity 10mo ago by Olin Lathrop‭

60%
+1 −0
Sensing 3 states in a single mcu pin using firmware

I want to sense 3 different states in the same mcu pin (GND, Hi-Z and PWR). PWR is typical +24V but I would like to have a wide margin from +17V to +40V just to be safe. The values can change but ...

1 answer  ·  posted 10mo ago by DeadMouse‭  ·  last activity 10mo ago by Olin Lathrop‭

75%
+4 −0
micro-RF connector crimping options

Do micro-RF connector mating crimp connectors are ever sold separately together with a crimp tool? For example this I have looked through a lot of pages, and can only find PCB connectors + cable a...

1 answer  ·  posted 10mo ago by Elleanor Lopez‭  ·  last activity 10mo ago by DSI‭

66%
+2 −0
Variant of a Mosfet's Gate-Source protection

Let's say a 100V voltage spike arrives at +12V and the TVS diode clamps it to 25V. Q2 may or may not be activated. Will this circuit ensure a V_gs lower than 25V for the mosfet Q1 ? Any catch to it...

1 answer  ·  posted 11mo ago by kellogs‭  ·  last activity 10mo ago by Olin Lathrop‭

60%
+1 −0
Synchronization of clock of satelite with devices here on the Earth

Serial communication protocols require synchronization of the clock of the connected devices. From GR the time elapsed for the satelite is different than the time elapsed for us here on the Earth....

1 answer  ·  posted 11mo ago by Volpina‭  ·  edited 11mo ago by Canina‭

57%
+2 −1
Understanding induction motors

I have been watching this video and at 3:28 it says that a induction is inherently self-starting.Does this happen because of the energy stored and released in the windings of the statorFrom 3:41 u...

0 answers  ·  posted 11mo ago by Volpina‭

60%
+1 −0
How is it possible to perform a open circuit test on a induction motor?

During the open circuit test of a induction motor ,not any current flows inside the rotor.But how can we achieve such a thing? Here is the ping configuration of a induction motor: The coils of ...

3 answers  ·  posted 11mo ago by Volpina‭  ·  last activity 11mo ago by rdtsc‭

66%
+2 −0
Oscillator with non-rechargable battery

Lets say I power an oscillator by a non-rechargable battery. Lets imagine a generic design with LC-circuit and negative resistance created by some transistor circuit. To me it seems that at certai...

1 answer  ·  posted 11mo ago by kek‭  ·  last activity 11mo ago by Olin Lathrop‭

60%
+1 −0
Contradiction between Routh's algorithm and checking with some value

I am designing a control system controlled by some microcontroller K: The open loop gain is $G_{o}(s) = \frac{K}{s(s^{2}+4s+3)}$ and the closed loop gain is obviously $G_{c}(s) = \frac{K}{s(s^{...

0 answers  ·  posted 11mo ago by Volpina‭

66%
+2 −0
Over-voltage protection for device with photovoltaic cell source

I have a solar panel rated for 6V open-circuit and up to 150mA. I would like to connect this to an SPV1040 or similar buck-boost converter with MPPT functionality to be able to charge a 3.6V batter...

2 answers  ·  posted 11mo ago by Keelan‭  ·  last activity 11mo ago by TonyStewart‭

75%
+4 −0
High Speed Digital Communication Bus Probing

For high-speed digital communication busses, what attributes do you generally advise to add to a PCB to help with validating the communication bus as well as troubleshooting the design? In particu...

1 answer  ·  posted 11mo ago by DavidE‭  ·  last activity 11mo ago by Olin Lathrop‭

66%
+2 −0
what should the output be for this use case of the CD4047 chip?

Hello, I am trying to use a CD4047 in monostable, positive-edge trigger mode: I am not skilled enough to make out what the output, i.e. pin 10, should be when pin 8, the input, is held at 0V (...

1 answer  ·  posted 11mo ago by kellogs‭  ·  edited 11mo ago by kellogs‭

50%
+1 −1
What are these transformer graphs about?

This picture describes the behaviour of a single phase transform under resistive,inductive and capacitive loads(from left to right) How what exactly is $V_{1}$ ?Is it the voltage at the primary ...

1 answer  ·  posted 11mo ago by Volpina‭  ·  last activity 11mo ago by TonyStewart‭

60%
+1 −0
Calculate values of externally excited DC generator/motor

We use a DC externally excited generator/motor as a generator.We excite the input of the generator and get at the output 10V at 1Wb flux and at 5rps generator speed without connecting the generator...

1 answer  ·  posted 12mo ago by Volpina‭  ·  last activity 11mo ago by Olin Lathrop‭

22%
+0 −5
edison and tesla [closed]

what diffrence between tesla and edison? can anyone help me who come first?

0 answers  ·  posted 11mo ago by kEKIVI‭  ·  closed 11mo ago by Mithical‭

71%
+3 −0
MOSFET protection with TVS: at the source pin or at the drain pin

In the auotmotive context, does it matter where the fat load-dump grade diode is placed in relation to the MOSFET so as to protect it from both fast positive transients and the longer load dump ? ...

2 answers  ·  posted 12mo ago by kellogs‭  ·  last activity 12mo ago by Lundin‭

50%
+2 −2
Role of C2 (bypass capacitor)

I have been reading about thermal noise in resistors and I have a question: Suppose we have this circuit: Is C2 here to protect the voltage source from thermal noise?

2 answers  ·  posted 12mo ago by Volpina‭  ·  last activity 12mo ago by Andy aka‭

71%
+3 −0
How can I fix this 4-20 mA current loop to source current that matches current sink on its input?

Building on a previous question about terminology, I am trying to arrive at a solution to connect a digital air pressure regulator that sinks current as part of its 4-20 mA current feedback loop to...

2 answers  ·  posted 1y ago by JYelton‭  ·  last activity 1y ago by Nick Alexeev‭

60%
+1 −0
What is the role of master clock speed on DAC

In protocol I2S we have 3 signal + one none standard master clock(Mentioined by Olin Lathrop): 1.data 2.lrck/fck (frame synchronizer) 3.bck (bit clock) 4.mck/sck (master clock) Question 1: Why we...

2 answers  ·  posted 1y ago by mohammadsdtmnd‭  ·  last activity 1y ago by mohammadsdtmnd‭

75%
+4 −0
Why arc welding does not require high voltage to arc?

I've heard that arc welding is getting done with low voltage. I believe arcing requires high voltage. Then how is arc welding done with about 50 volts? I thought we need kilovolts for arcing. Why? ...

3 answers  ·  posted 1y ago by mohammadsdtmnd‭  ·  last activity 1y ago by TonyStewart‭

71%
+3 −0
Is a current-dependent current source and a current mirror the same thing?

I have a 4-20 mA digital air pressure regulator which is controlled by and reports its pressure by being the current sink in two independent 4-20 mA current loops. Our control system utilizes Anal...

1 answer  ·  posted 1y ago by JYelton‭  ·  last activity 1y ago by Olin Lathrop‭

66%
+2 −0
Using arc trace routing instead of 45 degree trace routing

Most modern CAD software for PCB design offers arc trace routing or a form of conversion between 45/90 degree angel trace routing and arc trace routing. Despite this, the overwhelming majority of c...

3 answers  ·  posted 1y ago by Mu3‭  ·  last activity 1y ago by Lundin‭

66%
+2 −0
What does it mean for a signal to have impedance?

What does it mean for signals to have impedance? To me, impedance is kinda like an "extended resistance" that also includes phase shift $$Z = R + jX $$It makes sense to me that components like cap...

3 answers  ·  posted 1y ago by Carl‭  ·  last activity 1y ago by TonyStewart‭

71%
+3 −0
What is a good PCB-layout?

I am an electrical engineering student and I just finished designing an ECG-amplifier circuit. Here is the schematic: - It is fairly simple. Initially, there is a 1st order highpass filter. Then...

1 answer  ·  posted 1y ago by Carl‭  ·  last activity 1y ago by Olin Lathrop‭

71%
+3 −0
Testing instrumentation amplifier with differential signal

I am using the AD620 as instrumentation amplifier to amplify the body's ECG signal. An ECG is a differential signal (measured with two electrodes) and I want a differential gain of Gd=1000 . The ...

3 answers  ·  posted 1y ago by Carl‭  ·  last activity 1y ago by TonyStewart‭

50%
+1 −1
how to figure out the max power of a transformer?

I have a MOT that is rated 220V-50Hz only and i need to know its maximum operating power i tried to google the reference number but unable to find anything about its power, so how to figure out the...

2 answers  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Jasen‭

71%
+3 −0
How to check realistic specs of small solar panel?

I have a small solar panel rated for 6V/DC, 150mA. I know that those specs are under ideal circumstances, and I would like to do some measurements in different weather conditions to see what I can ...

3 answers  ·  posted 1y ago by Keelan‭  ·  last activity 1y ago by Olin Lathrop‭

33%
+0 −2
What we call this opamp configuration? [SOLVED]

1- What we call this opamp configuration? 2- What's the advantage and the disadvantage of this circuit? 3- And what's the purpose of the L2 in the feedback? I have changed gradually the value of...

1 answer  ·  posted 1y ago by deleted user  ·  edited 1y ago by deleted user

66%
+2 −0
Audio OpAmp requirements

As we know audio has high dynamic range. It means 120dB dynamic range of human ear causes to hear 1 million time samaller that highest undistorted accoustic wave. Then I think for high end audio we...

1 answer  ·  posted 1y ago by mohammadsdtmnd‭  ·  last activity 1y ago by Olin Lathrop‭

37%
+1 −3
Need help to replace 555

Hi guys, Can anyone help me please replace the NE555 IC in this circuit by MIC1555. I need to modify also the Voltage to 18v thank you. MIC1555 datasheet NE555 datasheet Edit: The circuit a...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Jasen‭

555