Download Resistor Calculator
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This calculator is based on the Ohms Law Calculator, but takes into consideration the voltage drop from the LED. To use the calculator, enter any three known values and press "Calculate" to solve for the others.
The specific parameters of the MOSFET, system voltage, and board parasitics will all affect the final VDS slew rate, so generally selecting an optimal value or configuration of external gate resistor is an iterative process. To help calculate the approximate gate resistor values with +/-30% accuracy, use the BLDC Gate Resistor Calculator.
To lower the gate drive current, a series resistor RGATE can be placed on the gate drive outputs to control the current for the source and sink current paths. A single gate resistor will have the same gate path for source and sink gate current, so larger RGATE values will yield similar SHx slew rates. Note that gate drive current varies by PVDD voltage, junction temperature, and process variation of the device.
Typically, it is recommended to have the sink current be twice the source current to implement a strong pulldown from gate to the source to ensure the MOSFET stays off while the opposite FET is switching. This can be implemented discretely by providing a separate path through a resistor for the source and sink currents by placing a diode and sink resistor (RSINK) in parallel to the source resistor (RSOURCE). Using the same value of source and sink resistors results in half the equivalent resistance for the sink path. This yields twice the gate drive sink current compared to the source current, and SHx will slew twice as fast when turning off the MOSFET.
A more complicated task is to pick resistors to satisfy a ratio. This is often done to set the division ratio in a voltage divider, for example. This is where the Resistor Ratio Calculator comes in handy.
There are four more or less commonly used resistor series, with 12, 24, 48, and 96 values per decade, respectively. Generally, 5% tolerance resistors are available in E24 and 1% resistors in E96, but this is not a hard and fast rule. For example some low-value 1% resistors are available in E12 only.
I am using the equation Qg = ig * t in order to calculate the gate resistor which charges the MOSFETs input capacitance (Ciss). The MOSFET I am using is the IRFP4368PBF. So if I use the equation Q=CV I can find the charge, in this case being (19860pF * 15V = 297.9nC). By rearranging (Qg = ig * t) to (ig = Qg / t) gives (297.9nC / t) . My question is that how do I find t , is it on the MOSFETs data sheet ? or else where ? because if i know t than i can calculated the current flowing into the MOSFETs gate which will than allow me to calculate the gate resistor.
Now your original question about the gate resistor value. It's a bit complicated. Higher resistor value will slow down turn-on but calculating how much time it will take to charge the gate up to Qg is always a big approximation as the MOSFET gate is not a constant value capacitor, and the MOSFET driver usually outputs a voltage, so using a fixed value resistor will result in high current during the beginning of turn-on, but as gate voltage increases then current will get lower... like in a RC circuit.
The purpose of the gate resistor is to prevent MOSFET oscillation, slow down switching if you want to avoid EMI problems, stuff like that. If you use a low frequency then slowing down the switching is an excellent way to reduce EMI. Some circuits use different resistors for turn-on and turn-off, with diodes or a dual-output driver ; this is a way to adjust switching times to avoid cross-conduction when using two FETs in synchronous mode.
Easy to use free and zero advertisement application which can do electronic color code calculation for 3, 4, 5 and 6 color bands resistors based on the latest IEC 60062:2016 standard. For every calculation, the nearest E6, E12 and E24 standard resistor values are displayed. To support the color-blind users, the color input buttons have text enabled on long click and the calculated color bands are also displayed in text format. Color code search by giving the numeric value and storage of up to 10 codes is also available. App can do SMD resistor value calculation based on 3- and 4-digit codes and EIA-96 code. App supports resistance calculations of parallel and series resistors. Resistance calculation of a conductor is also supported. Easy share and built-in help enabled.
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play.google.com Resistor Calculator - Color Code And SMDEasy to use free and zero advertisement application which can do electronic color code calculation for 3, 4, 5 and 6 color bands resistors based on the latest IEC 60062:2016 standard. For every calculation, the nearest E6, E12 and E24 standard resistor values are displayed. To support the color-blind users, the color input buttons have text enabled on long click and the calculated color bands are also displayed in text format. Color code search by giving the numeric value and storage of up to 10...
Color-coding is a method used to indicate the resistive value, tolerance, and temperature coefficient of resistors with low wattage rating because of their small size. Color bands are used because they can be easily and cheaply printed on a small electronic component. Color-coding is also used for capacitors, inductors and diodes.
When the resistor body surface is large enough, as in large wattage resistors, the resistance value, tolerance, and wattage are usually printed on the body of the resistor. Surface mounted resistors (SMD) use another coding system that uses alphanumeric codes printed on its surface instead of color codes.
In a three-band resistor, the first two bands represent the first two significant digits followed by one band for the multiplier. Since no tolerance band is available, the tolerance will always be 20%.
In a four-band resistor, which is the most common, the first two bands also represent the first two significant digits. The third band represents the multiplier. The fourth band represents the tolerance.
A zero-ohm resistor is a resistor having a single black band. Its resistance is approximately zero and it is used to connect two traces on a printed circuit board (PCB). Is it used in automated PCB assembly where using the same equipment used to mount other resistors is easier than using a separate machine to install a wire jumper.
If you need a non-standard resistor value you could probably realize a close match using two resistor. If you use two resistor in series it is quite easy to figure out which values give the best match; on the other hand, using a parallel connection it is not so easy (at least for me) to find a good combination.
This resistor calculation tool shows which combinations of two resistors (1______ or 2________) gives a match better than the closest standard value, for the E12 (10%), E24 (5%) and E96 (1%) series.
This VI takes an input of 3 different resistance band colors and calculates the resistance of the corresponding resistor. The VI utilizes case structures for each popssible color, and contains the value for the specific resistance. There is also a boolean indicator that will illuminate if an invalid color is typed in.
How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be \$3V/0.03A = 100 \Omega\$. However using software called Yenka, and trial and error I got the minimum possible resistance to be 36. However, if I use a 35 resistor, then the LED breaks. Is the software wrong, or (more likely) am I doing something wrong?
You'll have to check the datasheet or measure it to know how much voltage drops over your LED. Let's say this is 2V. Then the voltage over the resistor is the difference between your power supply (3V) - voltage over the LED (2V) = 1V. To get 30 mA through the resistor (and thus also the LED) your resistor has to be 1V / 30 mA = 33 Ohm.
If your LED voltage is lower the current will be somewhat higher, but the LED shouldn't break!
You bring up a good issue with a calculator though. Calculators generally don't handle units. They basically operate as if everything is a dimensionless quantity. This is where using the scientific notation capability of your calculator becomes very useful. To compute the resistance you do 3 / 30e-3. A value with a small exponents like 30e-3 might be easy to convert in your head to .030, but consider doing a computation with 22pF. 22e-12 is easy enough to enter, but what's the chance of getting .000000000022 right?
When you grapple with the concept of parallel resistors, you're not simply crunching numbers or going through the motions of a theoretical exercise. Instead, you're unlocking the potential to 3________________________________________________________________________________________________________________________
In a parallel circuit, resistors share the same voltage across them, a property that differs significantly from a series circuit. This unique behavior results in the total resistance of the circuit being lower than the smallest resistor in the parallel configuration. The ability to manipulate resistance values in this manner is crucial in various applications such as voltage division, impedance matching, and signal processing.
However, calculations of parallel resistance can often be challenging due to the complexity of the formula, especially when there are more than two resistors in the circuit. Therefore, to assist you, we have put together this guide to help you navigate parallel resistance calculations. So how do you accurately calculate the total resistance in a parallel resistor circuit? Let's look at the equations and a practical example to illustrate the process.
Parallel resistors, as the name suggests,4___________________________________________________________. This arrangement allows the current to have multiple paths to travel. It's a fundamental concept in electrical engineering as it allows us to manage and control how current is distributed in a circuit. 5376163bf9
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