Four types of MOS tubes
INDUSTRIAL LCD DISPLAYS / IGBT MODULES DISTRIBUTOR

Infineon / Mitsubishi / Fuji / Semikron / Eupec / IXYS

Four types of MOS tubes

Posted Date: 2024-01-17

The MOS tube in Figure 3.3.1 belongs to the N-channel enhancement type. This type of MOS tube uses a P-type substrate and the conductive channel is N-type. When vC5=0, there is no conductive channel and the turn-on voltage Vcs(u) is positive. Use a positive power supply when working, and the substrate should be connected to the source or the potential of the system. In the symbol given in Figure 3.3.1, the broken line segment between DS represents no conduction when Vcs=0.

The channel, that is, the MOS tube is enhanced type. The arrow on substrate B points to the inside of the MOS tube, indicating that the conductive channel is N-type. The gate terminal is drawn on the side close to the source.

2. P-channel enhanced type

Figure 3.3.6 is the structural diagram and symbol of a P-channel enhancement mode MOS tube. It uses an N-type substrate and the conductive channel is P-type. When vGS=0, there is no conductive channel. Only when a large enough negative voltage is applied to the gate, can the minority carriers-holes in the N-type substrate be attracted to the substrate surface below the gate, forming a P-type conductive channel. Therefore, the turn-on voltage Vcs(x) of the P-channel enhancement mode MOS transistor is negative. This kind of MOS tube uses a negative power supply when working, and the substrate needs to be connected to the source or the potential of the system.

The symbol of the P-channel enhancement mode MOS tube is as shown in Figure 3.3.6, where the arrow pointing outward on the substrate indicates that the conductive channel is P-type.

The switching circuit connected with P-channel enhanced MOS tube is shown in Figure 3.3.8.

When v =0, the MOS tube is not conducting and the output is low level. VoL. As long as R is much smaller than the cut-off internal resistance of the MOS tube, RorF, then. VoL = VvD.

When v1
1. N-channel depletion type

The structure of the N-channel depletion-mode MOS transistor is the same as that of the N-channel enhancement-mode MOS transistor. They both use a P-type substrate and the conductive channel is N-type. The difference is that in the depleted VpD-type MOS tube, a certain concentration of RD positive ions is doped into the silicon dioxide insulating layer under the gate. The electric field formed by these positive ions is enough to attract the minority carriers - electrons in the substrate to the substrate surface below the gate, forming a conductive channel between DS. Therefore, there is already a conductive channel when vCS=0. vC3 increases; when it is negative, the conductive channel v becomes wider, when v is positive, the conductive channel becomes wider, i vGS becomes narrower, and i decreases.

Until v is less than a certain negative voltage value VcS(eff), the conductive channel disappears and the MOS tube is turned off. V6S(eff) Figure 3.3.8 Pinch-off voltage of a P-channel enhancement type called N-channel depletion mode MOS transistor. Figure 3.3.9 of the switching circuit formed by connecting MOS tubes is the symbol of an N-channel depletion mode MOS tube. In the figure, DS is connected, indicating that a conductive channel exists when vCS=0. The remaining parts are drawn in the same way as the enhanced MOS tube. During normal operation, the substrate of the N-channel depletion mode MOS transistor should also be connected to the source or system potential.

2. P-channel depletion type

P-channel depletion-mode MOS transistors have the same structure as P-channel enhancement-mode MOS transistors. They are also N-type substrates and the conductive channel is P-type. The difference is that in the P-channel depletion mode MOS transistor, when vcs=0, there is already a conductive channel in vCs. When vcs is negative, the conductive channel further widens, and i increases; while when vCS is positive, the conductive channel narrows, and i decreases. When the positive voltage of (v) is greater than the pinch-off voltage Vcs(odf), the conductive channel disappears and the tube is turned off.

Figure 3.3.10 is the symbol of a P-channel depletion mode MOS transistor. During operation, its substrate should be connected to the source, or the substrate should be connected to the potential of the system.


#types #MOS #tubes