The study of analog I²C protocol the transistor, field effect tube, field effect tube drain gate open circuit

transistor is divided into two types of NPN and PNP type, except the power supply polarity of the different working principle is roughly the same. For the NPN tube, it is composed of 2 N-type semiconductor sandwiched a P-type semiconductor, the emission zone and the formation of the PN Junction between the base region is called the transmission junction, and the Collector zone and the base region formed by the PN Junction is called the junction, three leads are the emitter (Emitter), the basis (base) and collector C (Collector). When the B-point voltage is higher than the e-point voltage, the transmit junction is positive, and when the C-point voltage is higher than the B-point voltage, the collector junction is reversed, and the junction power supply is higher than the base power. In the manufacturing process, the free electron concentration in the transmitting area is more than that of the concentration zone, so at the positive bias voltage, the free electrons are diffused from the transmitting region to the base area, and the emitter current IE is formed. Because the base area is very thin, the electric junction of the inverse bias, the electrons into the base area, the first close to the junction near the dense, gradually forming an electron concentration difference, under the action of the concentration difference, prompting the electron flow in the base region to the collector junction diffusion, the electric field is pulled into the collector region to form a collector current IC. Due to the large junction and reverse voltage, the electrons are prevented from spreading from the collector to the base, and the electrons that are diffused to the collector junction are pulled back into the collector area to achieve amplification. The essence is that the transistor can control the large amount of change of the collector current with the small change of the base current . This is the most basic and most important feature of the transistor.

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FET is a voltage control element that uses the electric field effect generated by the input voltage to control the output current .

1. The junction-type FET consists of two pn junctions and a conductive channel, and three electrodes are D (drain drain), G (Gate grid), S (source), and the source and drain are interchangeable. Operating conditions: Two PN junction plus reverse voltage. Working principle: In the case of constant voltage between DS, change the source voltage of the GS inter-grid, through the change of PN Junction, control channel narrowing, that is, the size of the channel resistance, thereby controlling the drain current. When the gate source voltage is 0 o'clock, the current flowing is the maximum drain current. When the gate source voltage changes to a negative direction, the current flow gradually decreases, when the drain current is reduced to 0 o'clock, the corresponding voltage is the clamp power-off pressure.

2. Insulation type FET is a source and gate between the insulation layer of the field effect tube, called MoS Tube, features: high input resistance, low noise. It is also divided into depletion type and enhanced type. The depletion type is the addition of a large number of metal cations in the SiO2 insulating layer below the gate. So when ugs=0, these cations are already sensing the opposite layer, forming a channel. Therefore, as long as there is a drain source voltage, there is a drain current exists. When ugs>0, the ID is added further. Ugs<0, as UGS reduces the drain current gradually decreases until id=0. The corresponding id=0 of UGS is called clamp power-off pressure.

The enhanced structure is similar to depletion type. However, when Ugs=0 V, the voltage between D and S does not form a current between D and S. When the gate is added to the voltage, if 0UGS (th), the formation of a channel, the drain and the source to communicate. If the drain source voltage is added at this time, the drain current ID can be formed. When the ugs=0v is id=0, the leakage current will occur only after ugs>ugs (TH), which is called an enhanced MOS tube.

Field Effect Tube Drain gate circuit, pull-up resistor (10k) Action: If there is no pull-up resistor, when the Taki pass, the output is high, when the pipe cutoff time, the output is high. If a pull-up resistor is present, the output is low when the Taki pass, and the output is high when the pipe is cut off.

The study of analog I²C protocol the transistor, field effect tube, field effect tube drain gate open circuit