As shown in the figure above, this is a very common MOSFET switching circuit, RD is the load, RG is the internal resistance of the source, and it is also to protect the MOS transistor and the gate resistance in series to reduce the EMI problem. Then his opening waveform is as follows.
Observing the above two graphs, you will find that there is an obvious gap between the two IDs, one is that the graph I gave is increasing during the period when the VGS is basically unchanged, but the Maxim Semiconductor gives it remains the same, and his load is an inductor, and then the inductor current cannot be abruptly changed. However, the circuit diagram and waveform diagram of the resistive load used in some articles are still copied from Maxim Semiconductor, and the first step with the diagram is wrong.
Let's take a look at the waveform in Figure 2 under a resistive load.
T0 T1 Phase:
VIN for OV, VGS1 T2 stage:
The control voltage changes to vin, and we know that ucgd=vcc in the previous stage analysis of VGS at this stage. Because CDS is relatively small, then according to i=c*du dt, we can know that the current flowing through CDS is relatively small, and in order to analyze and derive the formula, a simplified circuit is obtained.
At this point, the IGD is:
So. 
Both sides are scored at the same time.
In this case, IRG1 is:
So. 
Both sides are scored at the same time.
It can be seen that the numerator of VGS1 increases with time, while the denominator decreases with time, that is to say, VGS1 increases with time, and the change is obvious.
where VGS1 and VGD1 represent the voltage charged on the capacitor at this stage, and the real voltage at both ends of the capacitor is:
At this time, the voltage of VDS, that is, the voltage of VD, is:
In the above formula, it can be found that VGS increases with time, VDS is higher than VCC, and the waveform is shown in the following figure.
T2 T3 Phase:
At T2, VGS increases to VTH, at which point the MOS tube starts to open, the current starts to flow, and the state occurs, i.e. VGS1=VTH as deduced earlier. And VDS > VGS-VTH, so now the MOS tube is in the constant flow region. The size of the id is:
At this time, there are two more stages, one is IGD2>ID and the second is IGD2
1) IGS > ID.
So. Both sides are scored at the same time.
In this case, IRG2 is:
So. Both sides are scored at the same time.
2) IGS So.
Both sides are scored at the same time.
At this time, IRG3 is:
So. Both sides are scored at the same time.
It is observed that VGS2 and VGS3 are much smaller than VGS1, which is the so-called plateau period, because the VGS changes smallly, so there is a plateau, and the small change of VGS in the constant current region will bring about a drastic change in ID. VGD2 and VGD3 were observed to vary greatly. That is to say, vd2=vgs2-vgd2 and vd3=vgs3-vgd3 are negative numbers, that is, vds is decreasing, and the waveform is shown below.
At this stage, the increase of VGS is very small, which leads to a drastic change in ID, and at the same time, it leads to a rapid change in VDS, which causes a rapid change in VGD, so the DT of DVGD is relatively large, so most of the current will flow to CGD, and CGS only has a small part of the current, so that VGS changes at a speed.
T3 T4 Phase:
At T3, VDS=VGS-VTH, that is, this stage officially enters the variable resistance region, and the RDS is relatively small, which can be equivalent to CGD and CGS being charged by VIN through RG in parallel. At this stage, the VGS will continue to rise until it becomes VIN, and the charging speed will be about the same as that of the T1 T2 stage, and the main CGS will dominate. cgs>>cgd。At this time, the RDS will decrease as the VGS increases, and when the VGS increases to a certain extent, the RDS will not decrease again, and will remain until RDS(on). When the RDS decreases, the ID will also increase, and when the RDS no longer changes, the ID will not change, and the waveform is as follows.
*The waveforms are as follows:
This is the process of analyzing the resistive load, and then the conduction process of the inductive load will be analyzed. One person cheers for the graduate school entrance examination