Detailed explanation and analysis of the working principle of E/DMOS inverter

E/D MOS inverter is the abbreviation of enhanced-depletion MOS inverter, which is a new circuit developed to improve the performance of MOS circuit. Its input tube is an enhanced device (referred to as EMOS tube), and the load tube is a depletion type device (referred to as DMOS tube). Figure 2-32(a) shows the circuit diagram of an N-channel E/D MOS inverter, where is the input tube, is the load tube. Since the gate and source of the load tube are connected together, the gate-source voltage of the load tube is always . Because of the original channel, the tube is always on. As the drain-source voltage of the load tube changes, it can work In the saturated zone, it can work in the unsaturated zone. Figure 2-32(b) shows a cross-sectional view of the structure of the E/D MOS inverter.

1. E/DMOS inverter working principle

If the inverter input voltage, the input tube is cut off, because its cut-off resistance is much greater than the channel resistance of the load tube, so the power supply voltage all falls on the input tube, making the output voltage of the inverter . If input voltage,The input tube is turned on, because the on-resistance is higher than the load The tube is much smaller, and the power supply voltage almost all falls on the load tube, so the output voltage is approximately 0V. In this way, the inverter has reached the "0" and "1" level conversion, completing the phase inversion function.

Same as the method of discussing E/EMOS, we can find two operating points in the on-state and off-state on the output characteristic curve. First, corresponding to the two states of inverter input "0" and "1", two output characteristic curves can be obtained. Then find a load line, and the two characteristic curves of the input tube intersect at two points A and B, which are the on-state operating point and the off-state operating point. As shown in Figure 2-33. The following describes how this load line is made.

As mentioned above, the load tube of the E/D MOS inverter is a depletion type device, and , so it has a corresponding output characteristic curve, as shown in Figure 2-34. E/DMOS inverter working principle, because the drain of the load tube is connected to a fixed power supply, the output voltage of the source connection change, therefore, take its coordinate origin as , add this characteristic curve to the two output characteristic curves of the input tube, and it becomes the load line of the E/DMOS inverter.

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