Current drain

The carriers in tire channel of an enhancement mode device exhibit unusually high mobility, particularly at low temperatures, a subject of considerable interest. The source-drain current is carried by electrons attracted to tire interface. The ionized dopant atoms, which act as fixed charges and limit tire carriers mobility, are left behind, away from tire interface. In a sense, tire source-drain current is carried by tire two-dimensional (2D) electron gas at tire Si-gate oxide interface. 

Tmoves to the left, reducing the effective channel length, but the drain current remains nearly constant. See text (26). 

Fig. 6. (a) Transfer characteristics of (b) i -Si TFT element. The drain current, / is plotted against the gate voltage, for three drain potentials A,... 

Figure 15-8 shows synchronous recordings of the voltage between the pipeline and the rails, of the pipe/soil potential f/cu cuso4 drained current in the region of a tramway transformer substation with and without various protective measures. Figure 15-8a records values without protective measures. If the rails are negative with respect to the pipeline (f/R s > 0), the pipe/soil potential becomes more positive. Stray current exit exists. From time to time, however, < 0. 

To control this loss one typically attempts to minimize the voltage drop across the power switch during its on-time. To do this, the designer must operate the switch in a saturated state. These conditions are given in Equations 4.2a and b. This is identified by overdriving the base or gate such that the collector or drain current is controlled by the external elements and not by the power switch itself. 

Stray current ( drained current ) Applicable only in proximity to stray d.c. areas ... 

Here, the flat-band potential was neglected.) A typical set of drain current-voltage curves for various gate voltages is shown in Figure 14-8. 

It is seen that for a given (constant) gate voltage, the drain current first increases linearly with the drain voltage (linear regime), then gradually levels off to reach a saturation value (saturation regime). 

Saturation turns on when the charge at drain vanishes, that is when Q(L) = 0. The saturation current can be estimated by following a method introduced by Brown and coworkers [I6 and developed further by Horowitz et al. [I7J. We assume that the accumulation layer extends from the source up to a point where V(x) — VK (sec Fig. 14-10), beyond which it turns to a depletion layer. The drain current is hence given by the sum of two integrals. 

Figure 14-27. Drain current-voltage charaeieristics of a doped DH6T OFET sliowiug both accumulation (V cO) and depletion (Fx>0) regimes.

The drain current /,/ is now calculated by estimating the channel conductance g... 

In a MESFET, a Schottky gate contact is used to modulate the source-drain current. As shown in Figure 14-6b, in an //-channel MESFET, two n+ source and drain regions are connected to an //-type channel. The width of the depletion layer, and hence that of the channel, is modulated by the voltage applied to the Schottky gate. In a normally off device (Fig. 14-9 a), the channel is totally depleted at zero gate bias, whereas it is only partially depleted in a normally on device (Fig. 14-9 b). 

Eq. (14.43) requires accumulation to extend all along the channel, namely Vdcontact with the rest of the semiconductor layer, we have also to account for the bulk conductivity of the semiconducting film when integrating the drain current, which leads to an equation of the form... 

Eq. (14.51) can be substantially simplified if we assume that C, 2> C which is indeed the case when the semiconducting film is thinner than the insulating layer. The drain current in the linear and saturation regimes is then respectively given by... 

Figure 14-23. Variation of the field-effect mobility, as deduced by differentiating the drain current at Vt,=-i V, as a function of the gale voltage, for the same device as in Figure 14-22.

Li-Mn02 batteries are available in a variety of shapes and construction [30] in accordance with their particular use. Figure 32 shows various applications of lithium batteries based on their drain current. Coin-type batteries are generally used for low-rate drain. Cylindrical batteries with the inside-out construction can serve as a... 

Figure 32. Various applications of lithium-manganese dioxide batteries, based of their drain currents.

FIGURE 6-20 Configuration of a penicillin sensor based on an microarray electrode coated with a pH-responsive polypyrrole. Vq = gate voltage VD = drain voltage ID = drain current PS = potentiostat CE and RE = counter and reference electrodes, respectively. (Reproduced with permission from reference 76.)... 

Fig. 7. Solid state molecular transistor based on polyaniline bridged microelectrodes. PVA layer of polyvinyl alcohol 1 drain current Vg gate voltage rendering the polyaniline non-conductive Vg gate voltage switching on conductivity of the polyaniline layer (from ref.

The operation principle of these TFTs is identical to that of the metal-oxide-semiconductor field-effect transistor (MOSFET) [617,618]. When a positive voltage Vg Is applied to the gate, electrons are accumulated in the a-Si H. At small voltages these electrons will be localized in the deep states of the a-Si H. The conduction and valence bands at the SiN.v-a-Si H interface bend down, and the Fermi level shifts upward. Above a certain threshold voltage Vth a constant proportion of the electrons will be mobile, and the conductivity is increased linearly with Vg - Vih. As a result the transistor switches on. and a current flows from source to drain. The source-drain current /so can be expressed as [619]... 

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