Depletion mode versus enhancement mode

The JFET works by varying the width of the channel. Normally the channel is wide open; as the depletion region gets wider and wider, choking off the channel, the charge carriers are forced to pass through a narrower and narrower path. This is known as the depletion mode of operation for a field-effect transistor.
A MOSFET can also be made to work in the depletion mode. The drawings and schematic symbols of Figs. 1 and 2 show depletion-mode MOSFETs.
However, MOS technology also allows an entirely different means of operation. An enhancement-mode MOSFET normally has a pinched-off channel. It is necessary to apply a bias voltage, E_G, to the gate so that a channel will form. If E_G = 0 in such a MOSFET, that is, if the device is at zero bias, the drain current I_D is zero when there is no signal input.

Fig. 1: At A, simplified cross-sectional drawing of an N-channel MOSFET. At B, the schematic symbol.

Fig. 2: At A, simplified cross-sectional drawing of a P-channel MOSFET. At B, the schematic symbol.

The schematic symbols for N-channel and P-channel enhancement-mode devices are shown in Fig. 3. The vertical line is broken. This is how you can recognize an enhancement- mode device in circuit diagrams.

Fig. 3: Schematic symbols for enhancement-mode MOSFETs. At A, N-channel; at B, P-channel.

مواضيع ذات صلة

الحساسات النانوية لرصد وتعقب حرائق الغابات

التكامل بين تكنولوجيا النانو وتكنولوجيا الاستشعار من بعد لرصد تلوث الهواء الجوي

الحساسات النانوية للحالة الصلبة

الحساسات النانوية لرصد ملوثات الهواء

تكنولوجيا النانو وصناعة الحساسات

الحساسات النانوية

تقنية النانو في الطباعة على الأسطح Nano–Lithography

تقنية الطباعة على الأسطح Lithography

التنافس العالمي في إنتاج الحاسبات المعتمدة على تكنولوجيا النانو

قانون مور

تركيب الترانزستور وكيفية عمله

ماهية الترانزستورات