1. Limit parameters:

ID: Maximum drain-source current. It refers to the maximum current allowed to pass between the drain and the source when the field effect tube is operating normally. The operating current of the field effect tube should not exceed ID. This parameter will be reduced as the junction temperature rises. .
IDM: Maximum pulse drain-source current. It reflects an impact resistance and is also related to the pulse time. This parameter will decrease as the junction temperature increases.
PD: Maximum dissipation power. It refers to the maximum drain-source dissipation power allowed when the performance of the field effect tube does not deteriorate. When used, the actual power consumption of the field effect tube should be less than the PDSM and leave a certain margin. This parameter is generally The amount decreases as the junction temperature rises. (This parameter is unreliable)
VGS: Maximum gate-source voltage., generally: -20V~+20V
Tj: Maximum operating junction temperature. Usually 150 ℃ or 175 ℃. Under the working conditions of device design, it is necessary to avoid exceeding this temperature and leave a certain margin. (This parameter is unreliable)
TSTG: storage temperature range

2. Static parameters

V(BR)DSS: Drain-source breakdown voltage. It refers to the maximum drain-source voltage that the field effect transistor can withstand when the gate-source voltage VGS is 0. This is a limiting parameter, and the operating voltage applied to the field effect transistor must be less than V(BR)DSS. It has positive temperature characteristics. Therefore, the value of this parameter under low temperature conditions should be considered for safety. It is better to add negative pressure.
△V(BR)DSS/ △Tj: Temperature coefficient of drain-source breakdown voltage, generally 0.1V/℃.
RDS(on): Under certain conditions of VGS (usually 10V), junction temperature and drain current, the maximum resistance between drain and source when the MOSFET is turned on. It is a very important parameter that determines the power consumption when the MOSFET is turned on. This parameter generally increases as the junction temperature increases (positive temperature characteristics). Therefore, the value of this parameter at the highest operating junction temperature should be used as the loss and voltage drop calculation.
VGS(th): Turn-on voltage (threshold voltage). When the external gate control voltage VGS exceeds VGS(th), the surface inversion layer of the drain region and the source region forms a connected channel. In applications, the gate voltage when ID is equal to 1 mA under the drain short-circuit condition is often called the turn-on voltage. This parameter generally decreases as junction temperature increases.
IDSS: Saturated drain-source current, the drain-source current when the gate voltage VGS=0 and VDS is a certain value. Generally in the microampere level.
IGSS: Gate-source drive current or reverse current. Due to the large input impedance of MOSFETs, IGSS is generally in the nanoamp level.

3. Dynamic parameters

gfs: Transconductance refers to the ratio of the change in drain output current to the change in gate-source voltage. It is a measure of the ability of the gate-source voltage to control the drain current. The transfer relationship between gfs and VGS is shown in the figure below.
Qgs: Gate source charging capacity.

 

Qg: Total gate charging capacity. MOSFET is a voltage-type driving device. The driving process is the establishment process of gate voltage. This is achieved by charging the capacitance between gate source and gate drain. This aspect will be discussed in detail below.
Qgd: Gate-to-drain charge (taking into account Miller effect).
Td(on): On-delay time. The time from when the input voltage rises to 10% to when VDS drops to 90% of its amplitude (refer to Figure 4).
Tr: rise time. The time for the output voltage VDS to fall from 90% to 10% of its amplitude.
Td(off): Off delay time. The time from when the input voltage drops to 90% begins to when VDS rises to 10% of its shutdown voltage.
Tf: fall time. The time it takes for the output voltage VDS to rise from 10% to 90% of its amplitude (refer to Figure 4).

Ciss: Input capacitance, Ciss= CGD + CGS (CDS short circuit).
Coss: Output capacitance. Coss = CDS +CGD.
Crss: Reverse transfer capacitance. Crss = CGD.
The last three formulas are very important

4. Avalanche breakdown characteristic parameters

These parameters are indicators of the MOSFET's ability to withstand overvoltage in the off state. If the voltage exceeds the drain-source limit voltage, the device will be in an avalanche state.
EAS: Single pulse avalanche breakdown energy. This is a limit parameter, indicating the maximum avalanche breakdown energy that the MOSFET can withstand.
IAR: avalanche current.
EAR: Repeated avalanche breakdown energy.

5. Thermal resistance

Thermal resistance from junction to case. It indicates the difference between junction temperature and case temperature when dissipating a given power. The formula expression is ⊿ t = PD* .
The thermal resistance from the shell to the radiator has the same meaning as above.
The thermal resistance from the node to the surrounding environment has the same meaning as above.

6. In vivo diode parameters

IS: Continuous maximum freewheeling current (from source).
ISM: pulse maximum freewheeling current (from source).
VSD: forward voltage drop.
Trr: Reverse recovery time.
Qrr: Reverse recovery charging capacity.
Ton: Forward conduction time. (Basically negligible).

7. Some other parameters:

Iar: Avalanche current
Ear: Repeated avalanche breakdown energy
Eas: Single pulse avalanche breakdown energy
di/dt---current rise rate (external circuit parameters)
dv/dt---Voltage rise rate (external circuit parameters)
ID(on)---on-state drain current
IDQ---quiescent drain current (RF power tube)
IDS---drain-source current
IDSM---maximum drain-source current
IDSS---Drain current when gate-source short circuit
IDS(sat)---channel saturation current (drain-source saturation current)
IG---Gate current (DC)
IGF---forward gate current
IGR---Inverse gate current
IGDO---when the source is open, the gate current is cut off
IGSO---when the drain is open, the gate current is cut off
IGM---gate pulse current
IGP---gate peak current
IF---diode forward current
IGSS---cut off the gate current when the drain is short-circuited
IDSS1---Drain-source saturation current of the first tube of the opposite tube
IDSS2---Drain-source saturation current of the second tube of the opposite tube
Iu---substrate current
Ipr---current pulse peak value (external circuit parameters)
gfs---forward transconductance
Gp---power gain
Gps---common source neutral and high frequency power gain
GpG---common gate neutral and high frequency power gain
GPD---common drain mid- and high-frequency power gain
ggd---gate-drain conductance
gds---drain-source conductance
K---offset voltage temperature coefficient
Ku---transmission coefficient
L---Load inductance (external circuit parameters)
LD---drain inductance
Ls---source inductance
rDS---drain-source resistance
rDS(on)---drain-source on-state resistance
rDS(of)---drain-source off-state resistance
rGD---gate-drain resistance
rGS---gate-source resistance
Rg---gate external resistance (external circuit parameters)
RL---Load resistance (external circuit parameters)
R(th)jc---junction-to-case thermal resistance
R(th)ja---junction ring thermal resistance
PD---drain power dissipation
PDM---Drain maximum allowable power dissipation
PIN--input power
POUT---output power
PPK---pulse power peak value (external circuit parameters)
Tj---junction temperature
Tjm---maximum allowable junction temperature
Ta---ambient temperature
Tc---tube shell temperature
Tstg---storage temperature
VGSF--forward gate-source voltage (DC)
VGSR---reverse gate-source voltage (DC)
VDD---Drain (DC) power supply voltage (external circuit parameters)
VGG---gate (DC) power supply voltage (external circuit parameters)
Vss---source (DC) power supply voltage (external circuit parameters)
V(BR)GSS---gate-source breakdown voltage when drain-source short circuit
VDS(on)---drain-source on-state voltage
VDS(sat)---drain-source saturation voltage
VGD---gate-drain voltage (DC)
Vsu---source substrate voltage (DC)
VDu---Drain substrate voltage (DC)
VGu---gate substrate voltage (DC)
Zo---drive source internal resistance
η---Drain efficiency (RF power tube)
Vn---noise voltage
aID---drain current temperature coefficient
ards---Drain-source resistance temperature coefficient

2. Characteristics that need to be considered in applications

1. Positive temperature coefficient characteristics of V ( BR ) DSS. This characteristic, which is different from bipolar devices, makes it more reliable when the normal operating temperature increases. However, it is also necessary to pay attention to its reliability during cold start at low temperatures.
2. Negative temperature coefficient characteristics of V (GS) th. The gate threshold potential will decrease to a certain extent as the junction temperature increases. Some radiation will also reduce the threshold potential, which may even be lower than 0 potential. This characteristic requires engineers to pay attention to the interference of MOSFET in these cases. False triggering, especially in MOSFET applications with low threshold potential. Due to this characteristic, it is sometimes necessary to design the off-voltage of the gate drive to a negative value (referring to N-type, P-type and so on) to avoid interference and false triggering. The threshold voltage is a negative temperature coefficient. In a radiation environment, the threshold voltage will quickly drop to 0. In order to turn off the MOS in a radiation environment, a backpressure needs to be added to GS. The switching speed (ie, slope) of MOS has nothing to do with temperature, but the turn-on (the time from 0V to Vgsth is called conduction delay) and turn-off delay are related to temperature. The higher the temperature, the shorter the time.
3. Positive temperature coefficient characteristics of VDSon/RDSon. The characteristic that VDSon/RDSon increases slightly as the junction temperature increases makes it possible to directly use MOSFETs in parallel. Bipolar devices are just the opposite in this respect, so their parallel use becomes quite complicated. RDSon will also It increases slightly with the increase of ID. This characteristic and the junction and surface RDSon positive temperature characteristics allow MOSFET to avoid secondary breakdown like bipolar devices. MOS with high rated voltage have higher RDSon positive temperature characteristics. temperature characteristics.
However, it should be noted that the effect of this feature is quite limited. When used in parallel, push-pull or other applications, you cannot completely rely on the self-regulation of this feature. Some fundamental measures are still needed.
This characteristic also shows that the conduction loss will become larger at high temperatures. Therefore, special attention should be paid to the selection of parameters when calculating the loss.
4. Negative temperature coefficient characteristics of ID
ID will derate considerably as the junction temperature increases. This characteristic makes it often necessary to consider its ID parameters at high temperatures during design.
5. Negative temperature coefficient characteristics of avalanche capability IER/EAS. After the junction temperature increases, although the MOSFET will have a larger V (BR) DSS, it should be noted that the EAS will be significantly derated. In other words, its ability to withstand avalanches under high temperature conditions is weaker than that at normal temperature. a lot of.
6. The conduction capability and reverse recovery performance of the parasitic diode in the MOSFET are no better than that of ordinary diodes. In the design, it is not expected to be used as the main current carrier of the loop. Blocking diodes are often connected in series to invalidate the parasitic diodes in the body, and additional parallel diodes are used to form the loop current carrier. However, during short-term conduction or some small currents such as synchronous rectification, It can be considered as a carrier if required.
7. The rapid rise of the drain potential may cause spurious-triggering of the gate drive. Therefore, this possibility needs to be considered in large dVDS/dt applications (high-frequency fast switching circuits).
The relationship between Rth(j-c) and PD, Tc (ambient temperature) = Tj-Rth(j-c)*PD

In turn, it can be deduced that every time the environment increases by one degree, the PD decreases. (This parameter is unreliable)
Main parameters (Higher Education Press Edition)
1. Turn on voltage VT
·Turn-on voltage (also called threshold voltage): the gate voltage required to start a conductive channel between the source S and the drain D;
·Standard N-channel MOS tube, VT is about 3~6V;
·Through process improvements, the VT value of the MOS tube can be reduced to 2~3V.
2. DC input resistance RGS
·That is, the ratio of the voltage applied between the gate and the source to the gate current
·This characteristic is sometimes represented by the gate current flowing through the gate.
·The RGS of the MOS tube can easily exceed 1010Ω.
3. Drain-source breakdown voltage BVDS
·Under the condition of VGS=0 (enhanced mode), the VDS when ID starts to increase sharply during the process of increasing the drain-source voltage is called the drain-source breakdown voltage BVDS
·The reasons for the sharp increase in IDs are as follows:
(1) Avalanche breakdown of the depletion layer near the drain
(2) Punch-through breakdown between drain and source
·In some MOS transistors, the channel length is short. Increasing VDS will cause the depletion layer in the drain region to extend to the source region, making the channel length zero, that is, a punch-through between the drain and the source will occur. After the punch-through, the source region The majority carriers in will be directly attracted by the electric field of the depletion layer and reach the drain region, resulting in a large ID
4. Gate-source breakdown voltage BVGS
·In the process of increasing the gate-source voltage, the VGS when the gate current IG increases sharply from zero is called the gate-source breakdown voltage BVGS.
5. Low frequency transconductance gm
·Under the condition that VDS is a certain fixed value, the ratio of the microvariation of the drain current to the microvariance of the gate-source voltage that causes this change is called transconductance
·gm reflects the ability of the gate-source voltage to control the drain current
·Is an important parameter characterizing the amplification capability of MOS tubes
·Generally in the range of a few tenths to several mA/V
6. On-resistance RON
·On-resistance RON illustrates the influence of VDS on ID and is the reciprocal of the slope of the tangent line at a certain point of the drain characteristic.
·In the saturation zone, ID hardly changes with VDS, and the value of RON is very large, generally between tens of kiloohms and hundreds of kiloohms.
·Since in digital circuits, MOS tubes often work in the state of VDS=0 when they are turned on, so the on-resistance RON at this time can be approximated by the RON at the origin.
·For general MOS tubes, the value of RON is within a few hundred ohms.
7. Interelectrode capacitance
·There are interelectrode capacitances between the three electrodes: gate-source capacitance CGS, gate-drain capacitance CGD and drain-source capacitance CDS
·CGS and CGD are about 1~3pF
·CDS is about 0.1~1pF
8. Low frequency noise coefficient NF
·Noise is caused by irregularities in carrier motion inside the tube
·Due to its existence, an amplifier will experience irregular voltage or current changes at the output end even when there is no signal input.
·The size of the noise performance is usually expressed by the noise coefficient NF, whose unit is decibel (dB)
·The smaller this value is, the smaller the noise generated by the tube is.
·Low-frequency noise figure is the noise figure measured in the low-frequency range
·The noise coefficient of the field effect transistor is about a few decibels, which is smaller than that of the bipolar transistor.
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