At a particular voltage level, which we will shortly define as the threshold voltage, the electron density at the surface exceeds the hole density. As the voltage on the top electrode increases further, electrons are attracted to the surface. The characteristics of an nMOS transistor can be explained as follows. MOSFET output characteristics plot I D versus V DS for several values of V GS. (2): Circuit symbols for nMOS and pMOS respectively Output Characteristics of MOSFET: Figure 1 shows the schematic diagram of the structure of an nMOS device before and after channel formation.ДЇigure 2, shows symbols commonly used for MOSFETs where the bulk terminal is either labeled (B) or implied (not drawn). The channel can be of n-type or p-type, and is accordingly called an nMOSFET or a pMOSFET. In MOSFETs, a voltage on the oxide-insulated gate electrode can induce a conducting channel between the two other contacts called source and drain. VIH can be recognized by the analog switch as the minimum level of logic high VIL can be recognized by the analog switch as the maximum voltage of logic low.The metalвЂ“oxideвЂ“semiconductor field-effect transistor (MOSFET) is a transistor used for amplifying or switching electronic signals. If the impedance of the front-end circuit is small, the effect of on-resistance will be greater. It should be noted that if the impedance of the front-end circuit through the analog switch is large, the effect of leakage current cannot be ignored. Generally, the smaller the leakage current, the better. If the internal resistance of the signal source is very high and the transmission signal is DC, it is particularly necessary to consider the leakage current of the analog switch. When the switch is off, the leakage current will flow into the load, causing additional errors. The current is not zero, and the conventional CMOS leakage current is about 1nA. Leakage Current: A switch in an ideal state requires zero resistance in the on-state, and the on-resistance in the off state tends to be infinite, and the leakage current is zero in fact, the switch is in a high-impedance state when it is off, and the leakage current is zero. After the two resistors are connected in parallel, they are relatively low in the effective range of the entire signal. The on-resistance of the NMOS tube is small when the signal is relatively low, while the on-resistance of the PMOS tube is small when the input signal is high. The advantage of CMOS switches is the rail-to-rail dynamic range, bidirectional operation, and the on-resistance remains unchanged when the input voltage changes. The two MOSFETs are turned on or off under the control of internal inverting and non-inverting logic. Since the switch does not have the problem of selecting the direction of current flow, there is no distinction between input and output. The amount of signal current carried between NMOS and PMOS is determined by the ratio of input to output voltage. Due to the different characteristics of PMOS and NMOS, the switch composed of them has the characteristics shown in the figure below. NMOS turns on when Vgs is positive, and turns off when Vgs is negative, and PMOS does the opposite. The gate is used to control the turn-on and turn-off of the switch. Connecting NMOS and PMOS in parallel allows signals to pass equally smoothly in both directions. The structure of the traditional CMOS process analog switch is shown in Figure 1. Because of its low power consumption, fast speed, no mechanical contacts, small size and long service life, it has been widely used in various automatic control systems and electronic digital products. An analog switch is a switch that uses the characteristics of JFET or MOS to control the signal path, and is mainly used to complete the switching function of signal link connection or disconnection.

Pmos and nmos ioff current