Take a look at MOSFETs

MOSFETs are insulating MOSFETs in integrated circuits.MOSFETs, as one of the most basic devices in the semiconductor field, are widely used in board-level circuits as well as in IC design.The drain and source of MOSFETs can be interchanged, and are formed in a P-type backgate with an N-type region. In general, the two sources are interchangeable, both forming an N-type region in the P-type backgate. In general, these two zones are the same, and even if these two sections are switched, the performance of the device will not be affected. Therefore, the device is considered to be symmetric.

Principle:

MOSFET uses VGS to control the amount of "induced charge" to change the condition of the conductive channel formed by these "induced charges" to control the drain current. When MOSFETs are manufactured, a large number of positive ions appear in the insulating layer through special processes, so that more negative charges can be sensed on the other side of the interface, and the N-region of the high-permeability impurities is connected by these negative charges, and the conductive channel is formed, and a relatively large drain current, ID, is generated even if the VGS is 0. If the gate voltage is changed, the amount of induced charge in the channel also changes, and the width of the conductive channel changes to the same extent. If the gate voltage changes, the amount of induced charge in the channel will also change, and the width in the conducting channel will also change, so the drain current ID will change along with the gate voltage.

Role:

1. It can be applied to the amplifier circuit. Because of the high input impedance of the MOSFET amplifier, the capacitance of the coupling can be smaller and electrolytic capacitors can not be used.

High input impedance is suitable for impedance conversion. It is often used for impedance conversion in the input stage of multi-stage amplifiers.

3、It can be used as variable resistor.

4, can be used as an electronic switch.

MOSFETs are now used in a wide range of applications, including high-frequency heads in televisions and switching power supplies. Nowadays, bipolar ordinary transistors and MOS are compounded together to form IGBT (insulated gate bipolar transistor), which is widely used in high-power areas, and MOS integrated circuits have the characteristic of low power consumption, and now CPUs have been widely used in MOS circuits.