Why is the parameter of this MOS tube, which is the relationship between V GSth and TJ temperature, still conditional on VGS=VDS?

小太阳yy

Why is the parameter of this MOS tube, which is the relationship between V GSth and TJ temperature, still conditional on VGS=VDS? [Copy link]

 

 

Why is the parameter of this MOS tube, which is the relationship between V GSth and TJ temperature, also has the condition VGS=VDS? Why is there this condition?

Also, why is there a condition VDS=-6v in the relationship between ID and VGS below? This is not right. When fully turned on, isn't the internal resistance between DS very small? More than 10mΩ, so why is the voltage so high at -6V?

qwqwqw2088

VGS(th) is a negative temperature coefficient. When the temperature rises, the MOSFET will turn on at a relatively low gate-source voltage.

You can first understand that the threshold voltage or turn-on voltage of the VGS value is represented by VGS (th).

maychang

"Why is there a condition VGS=VDS for the parameters of this MOS tube, which is the relationship between V GSth and TJ temperature? Why is there such a condition?"

The MOS tube turn-on voltage is not only affected by temperature, but also by the drain voltage. Of course, the test conditions need to be specified.

This regulation actually connects the gate and drain together, applies a fixed current to the gate, measures the voltage on the gate, changes the temperature, and measures the turn-on voltage at another temperature.

maychang

"And the relationship between ID and VGS below, why is there a condition VDS=-6v? This is not right, isn't the internal resistance between DS very small when fully turned on? More than 10mΩ, how can the voltage be as high as -6V?"

Why don't you see that the drain current is already hundreds of amperes? Moreover, the MOS tube is not fully turned on at this time.

小太阳yy

qwqwqw2088 published on 2022-9-19 07:31 VGS(th) is a negative temperature coefficient. When the temperature rises, the MOSFET will turn on at a relatively low gate-source voltage. You can first understand the threshold value of VGS value...

My friend, your answers are always inconsistent with what I asked. You perfectly avoid my questions. Haha.

小太阳yy

maychang published on 2022-9-19 12:04 『Why is there a condition VGS=VDS for the parameters of this MOS tube, which is the temperature relationship between V GSth and TJ? Why is there such a condition? 』 ...

When you say the turn-on voltage is affected by the drain voltage, is it affected by the drain-to-ground voltage or the voltage between DS?

小太阳yy

maychang posted on 2022-9-19 12:06 『Also, the relationship between ID and VGS below, why is there a condition VDS=-6v? This is not right either. When fully turned on, the internal resistance between DS is not very small...

Now I don't understand whether the voltage between DS is intentionally added or when the voltage between GS reaches a certain value, DS is always 6V after such a large current passes through? Who controls the current?

maychang

小太阳yy posted on 2022-9-19 12:17 When you say the turn-on voltage is affected by the drain voltage, is it affected by the drain-to-ground voltage or the voltage between DS?

"The turn-on voltage is affected by the drain voltage. Is it affected by the drain-to-ground voltage or the voltage between DS?"

is the voltage between drain and source.

However, when testing V GSth, the signal is the voltage from gate to source, so the source is the common terminal of input and output, and the source can be regarded as "ground".

maychang

小太阳yy posted on 2022-9-19 12:19 Now I don’t understand whether the voltage between DS is intentionally added? Or when the voltage between GS reaches a certain value, after such a large current passes, DS will...

"I don't understand now whether the voltage between DS is intentionally added? Or when the voltage between GS reaches a certain value, DS is always 6V after such a large current passes through it? "

It is of course added externally and remains constant during the measurement process.

maychang

Xiaoyangyy published on 2022-9-19 12:19 Now I don't understand whether the voltage between DS is intentionally added? Or when the voltage between GS reaches a certain value, after such a large current passes through DS...

"Who controls the magnitude of this current?"

In the second picture of the first post, the horizontal axis is V GS and the vertical axis is ID . In mathematics, the horizontal axis is usually defined as the independent variable and the vertical axis as the function. Who controls ID ?

小太阳yy

maychang posted on 2022-9-19 12:28 小太阳yy posted on 2022-9-19 12:19 Now I don’t understand whether the voltage between DS is intentionally added? Or when the voltage between GS reaches a certain level...

Can I understand it this way? Teacher, when I use MOS as a switch, the voltage between gs determines the size of the internal resistance between ds, and the current between ds is the current determined by the external control circuit. This current and the resistance determine the size of the voltage between ds. Is this correct? If the voltage between gs cannot reach the conduction voltage, then the current of the external circuit will be very small and cannot go up. Is this what you mean?

maychang

小太阳yy posted on 2022-9-19 13:09 Can I understand it this way? Teacher, when I use MOS as a switch, the voltage between gs determines the size of the internal resistance between ds, and the current between ds is outside...

"When I use MOS as a switch, the voltage between Gs determines the size of the internal resistance between DS, and the current between DS is the current determined by the external control circuit. This current and resistance determine the size of the voltage between DS. Is this understanding correct?"

When the N-channel MOS tube is used as a switch, the voltage between GS is either very small (close to zero or even negative), in which case the MOS tube is turned off and the resistance between DS is very large, or it is large enough (much larger than VGSTH but less than the allowable value), in which case the MOS tube is fully turned on and the resistance between DS is very small.

When the MOS tube is used as a switch, the current between DS is either very small (the MOS tube is turned off) or determined by the external circuit (power supply and load) (the MOS tube is fully turned on). When the MOS tube is fully turned on, the voltage between DS should be very small (determined by the current and the on-resistance of the MOS tube, and is no longer controlled by the voltage between GS).

maychang

小太阳yy posted on 2022-9-19 13:09 Can I understand it this way? Teacher, when I use MOS as a switch, the voltage between gs determines the size of the internal resistance between ds, and the current between ds is outside...

"If the voltage between gs cannot reach the conduction voltage, then the current in the external circuit will be very small and will not increase. Is that what you mean?"

That's what I mean.

maychang

小太阳yy posted on 2022-9-19 13:09 Can I understand it this way? Teacher, when I use MOS as a switch, the voltage between gs determines the size of the internal resistance between ds, and the current between ds is outside...

"If the voltage between gs cannot reach the conduction voltage, then the current in the external circuit will be very small and will not increase. Is that what you mean?"

Of course, if the voltage between GS is large enough, if the voltage between DS is very small (determined by the external circuit), the current will not increase. However, the effect of the voltage change between GS on the D-pole current is much greater than the effect of the voltage change between DS on the D-pole current within a certain range.

小太阳yy

maychang posted on 2022-9-19 14:13 "If the voltage between GS cannot reach the conduction voltage, then the current in the external circuit will be very small and cannot go up. Is that what you mean?" Of course, GS...

I understand, teacher. Thank you.