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# Questions tagged [current]

Flow of electric charge - typically movement of charge carriers, such as electrons. Measured in amperes (A).

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30 views

### For a bandpass transfer function, are there two gain bandwidth products?

Every example I have come across shows the gain bandwidth product used only for low pass transfer functions, but I never see it used for bandpass or in fact high pass transfer functions. Why is this?
722 views

### What is the name of this current called in this regulator datasheet?

Which parameter in this data sheet is the default current flowing from the input to the ground regardless of the load current? In my case an 12V input will be regulated to 5V by the TL780-05. So to ...
38 views

### Is it safe to make common ground between multiple voltage planes

I have a system where I have two power inputs and a single power output. One input from a battery(13v, 10A max) and one from solar cells(19v, 10A max). Then there is an 12v output which I connect to a ...
39 views

### sensing current noninvasively using hall effect sensors

I am trying to sense if DC current increases in a wire when the load changes. I do not care about the value of the current, I only want to know if it increases (motor at idle vs motor running). I ...
53 views

### Measuring high currents with toroids

I got a PT27312 current sensor (datasheet), I wonder if I can use it to measure currents up to 100A AC/DC. I couldn't find any specifications in respect of the current measurement range. I only know ...
36 views

### How to calculate current sink

Below schematic is what I have on the breadboard: simulate this circuit – Schematic created using CircuitLab R1 is there to sink 10mA of current to bias LM317, but 470 ohm is a value that I ...
92 views

### Does current flow across 0 resistance and 0 potential difference?

For the following circuit, will current flow from 3' to 3. I know that both are at 0V. However, the resistance between 3' to 3 is 0 ohms. So, ohms law would give the current as 0/0 which is ...
77 views

### How does this circuit work (opentherm)?

I am trying to understand how this data interface works. It's supposed to: translate (read) "OT" current difference into logical OUT (<10mA = 0, >17mA = ...
740 views

### Meaning of “pulse duration” in transistor datasheets?

I have a somewhat basic question. Many transistor datasheets have something like this for the peak current: pulse duration = 300 μs, duty cycle ≤ 1 % What does pulse duration mean? Is it only the on ...
62 views

### Opamp Current Sink + FET circuit help

I've been trying to figure out a design someone made for controlling a precision high current LED, and it's got me in a bit of a pickle. For the life of me, I can't figure out this exact op amp ...
31 views

### What is the maximum current can pass in BQ40Z50R2 (fuel gauge IC?)

I am unable to find the maximum current this fuel gauge IC can pass from its datasheet. Can anyone tell me?
21 views

### What is the current limitation of lenovo c340 USB port? [closed]

How much DC current can I "ask" of the lenovo c340 before it's damaged? Will it cut the supply on its own? at what conditions? what current is the max for a long time and what is the allowed peak?
21 views

### Inrush current and number of devices per MCB

I'm looking at some LED drivers meant to be powered by the regular mains voltage (230V). The datasheet specifies how many drivers can be connected to a single Miniature Circuit Breaker (MCB) on ...
76 views

### Current and resistance

Can anybody explain why my tongue gets a reading on a multimeter. Do I have a current? Why do i have resistance? Why do some things have resistance? I am very confused.
85 views

### Total current current equation in P-N junction

So Okay I get why there is a negative sign in the equation for diffusion current of holes since the gradience is actually negative if we put our coordinate axis in the bottom left corner for example ...
52 views

### Find current in the s-domain with 12V dc source

Notice my edit below I am trying to find the current i(t) that goes through the inductor in the s-domain. I know that it can be done the following way: $$I(s)=\frac{Y_1(s)}{Y_{eq}(s)}\cdot I(s)$$ ...
100 views

### Is there a proof of the following statement?

I am reading Electronic Principles by P.E. Gray and C.L. Searle and I came across the following statement. If there are n capacitors and no capacitor loops, the highest power of s in the ...
127 views

### Will current usage increase with different length of wire? [closed]

Given all other factors are same, with only the wire length increased (for example, 0.5meter increase to 50 meters,) will the current consumption/usage increase as well? Can anyone explain?
33 views

### Correct way of calculating BLDC torque for a given RPM and Current

A permanent-magnet 3-phase brushless DC electric motor is attached to a load. Motor is operated with vESC6.6 inverter, which is software-limited to 140A. Measured efficiency at maximum power is 81%. ...
56 views

### Current through a transistor

I have a problem related with a transistor circuit. Please tell me whether my approach is correct or not. I need to find the current through the 94.6ohms transistor. My approach (Assuming PN voltage ...
45 views

### Inverted Op Amp for Current Sensor Output

I'm having trouble understanding why the following circuit uses the inverting configuration rather than the non-inverting configuration for amplification. This design is from the Sparkfun Current ...
37 views

### Finding the maximum current

So, we did our lab activity and I don't quite understand the question "How could the circuit be modified so that the maximum current could be set to a value higher than that achieved by the supply ...
62 views

### using current limiting diodes instead of resistors

Most 3d printers have stepper motors that are rated for maybe 2-3 volts, but are usually driven at much higher voltage like 12 or 24 volts. It's possible since the motor drivers are current limiting - ...
103 views

### Output stage using 2 transistors

I want to understand how does this 2-transistor circuit work. It is used in a schematic for increasing the current rating at the discrete output stage. This does not look like a standard darlington ...
24 views

### Connecting multiple LED strips in parallel to a 220v/5A power line (via 12V driver)

I would like to power 5 LED strips via a 220v/5A wall outlet (each strip is 5m in length). I will be consulting and employing the electrician for the best way to run the wiring but from the initial ...
25 views

### Interface conditions and surface current density

let's consider the interface condition for magnetic field strength: 1) I do not have a clear idea of what js represents. If I have understood it correctly, it is a linear density ([A/m]) of a surface ...
64 views

### How do I find the equivalent circuit of a compensated attenuator?

I can not find the equivalent circuit due to the wire joining the middle of the resistor branch and the capacitor branch.
88 views

### Why is my Transformer pulling so much current?

I have taken a microwave oven transformer and removed the 2nd winding which originally put out 2000 volts. I have rewound the 2nd coil to produce 21 VAC which I then rectify and smooth with 2 large ...
34 views

### How do I solve the input resistance of this BJT and MOSFET in series?

This is a sedra-smith microelectronics excercise question for which I can not find the answer and I hoped for perhaps a solution here?
29 views

### Hall effect current sensor and proximity to EMI

I am preparing to layout a PCB. I have an ACS723, that I want to use to sense the current going through a relay. In addition to the relay I have a Meanwell IRM-12-20 to supply ac to dc voltage to the ...
72 views

### why the voltage at the gate terminal is 1.8V irrespective of the 3.3V pull up? [closed]

[![the output of my GPIO is 1.8V which is pulled up to 3.3V using a 4.7K resistance and that gpio is connected to the gate terminal of a P-channel mosfet, when i measure voltage across the gate ...
41 views

### Changeover relay circuit

I am looking for a circuit for one of mine typical application. I have transformer power supply with 230VAC/DC input with 12V /1A and 5V/500mA output. Now I wanted to introduce another stand by power ...
64 views

### Phase difference between resistor and inductor voltage in an RL AC circuit

In my textbook, it is given that $\mathcal {E} = -L\frac{\Delta I}{\Delta t}$. The graph of resistor voltage ($V_R$) and inductor voltage ($V_L$) in a series RL AC circuit is given similar to ...
111 views

### Is there a derivation of the Early effect?

I can't seem to find a derivation of the following equation: $$I_C=I_Se^{\frac{V_{BE}}{V_{T}}}\left(1+\frac{V_{CE}}{V_A}\right)$$ Is there a way to derive this equation? Edit: The equation ...
56 views

### amplify/increase current from 9v battery

I have a working circuit that generates a signal (a range of slow and fast tones) and sends them to a speaker. I tried to switch to a piezo driver and speaker and was successful using the MAX9788 as ...
32 views

### Low power rectification of AC component of modulated current signal

I have a current source consisting of a 100Hz sine plus a DC offset: $I=I_{DC}+I_{AC}\cdot\sin(2\cdot\pi\cdot 100Hz\cdot t)$ with $I_{DC}\approx100uA$ and $I_{AC}\approx 1uA$. I would like to ...
32 views

### Diffusion current causes drift current?

I was studying about currents in an injected semiconductor (by illumination) from Integrated Electronics by Millman and Halkias. They consider the diffusion hole current in an injected n-type open-...
80 views

### BJT Circuit Current

I have a question regarding the circuit below. I am unsure how to calculate the current flowing through the 1k resistor. I think it is reasonable assumption that the collector of the PNP BJT must ...
103 views

### Is the electric current delayed

simulate this circuit – Schematic created using CircuitLab -Suppose that the distance between "D1" and "D2" is too large. -Does "D2" give a delayed response compared to "D1"?
63 views

### Reverse Current building up Voltage

Just wanted to clarify my understanding before I design my circuit. This is based on my previous question I have an 3.3V LDO Regulator. Vin = Regulated 5V Vout = 3.3V Load Current = 100mA. At ...
43 views

### Why do people waste time using a SPICE .NOISE analysis for circuits with resistances with significant excess noise?

Refer to Resistor Current Noise Measurement Excess noise in a resistor is the electrical noise which is in excess of the value predicted by the well-known Johnsson-Nyquist-Thermal noise formula. ...
91 views

### How can I get/build a current controller/amplifier?

Background: I have a Lorenz-actuator (coil+magnet) that I need to control precisely using a computer. The computer signal is output from a dSpace microLab box as an analog ±10V signal. This signal ...
50 views

### Switch current rating label: 0.1GPA

I feel like this ought to be a FAQ, but because of the abundance of articles on Grade Point Average coming out of the US, it's extremely difficult to search for. I have a micro switch with rather ...
43 views

### Choosing a current sensor based on mV per amp

I want to measure AC current with an Arduino-type device. I am currently selecting a current sensor. A 10 bit ADC gives 1023 points. At 5v that is 5v/1023 = 4.9mV A current sensor with 185mV/A thus ...
123 views

### Transformer Welfare

I know this circuit is dangerous, but i made it anyway (probably a mistake)-https://www.instructables.com/id/Variable-voltage-ignition-coil-power-supply/ In my circuit, I used a small ignition coil ...
159 views

### voltage regulator current draw

I have a question about the operation of a voltage regulator. The supply is 12V and can provide 15W (max current draw 1.25A). Now when I use a linear voltage regulator down to 5V do the 15W still ...
58 views

### Buck converter source current draw

I'm doing some calculations for a system that is going to use a few buck converters. I need to make sure that the battery will be able to feed enough current but I'm not 100% certain how power on the ...
54 views

### DC Power Supply maximum current

let's consider a DC power supply of 5V with for instance 1A of maximum output current (i.e. its maximum output power if 5W). Let's connect a load R = 1 Ohm. Ideally a voltage source of 5V will give ...