Output Curve of Field Effect Transistor
Example 1 of output curve of field effect transistor:
Question:As shown in the figure,when Vgs = 8V and Vds = 20V,the Id is close to 300A. How did the data be tested?You know I put the 12V voltage between D and S,and the tube burst in an instant.
Output Curve of Field Effect Transistor (Example Interpretation)
Answer:Some of the curves you see refer to the ideal current curve when the core package is unrestricted and the core temperature is constant at 25 C.IR is generally tested, and MOS in China is not tested,basically a theoretical curve.But TO220 or other encapsulated MOS are limited by encapsulation.There are two kinds of actual Id sizes:one is limited by encapsulation,the other is limited by core temperature.You can refer to the application notes of IR official network before doing this experiment,or according to the test conditions on pdf.As you said,it is generally not feasible.If the current of 12V test power supply is large enough,when MOS is fully turned on,its Id will be very high,which will lead to excessive power consumption damage of mos,so your experiment is meaningless.
In addition,the field effect transistor G pole can not be suspended. Otherwise,it is very easy to make the tube open because of the induced voltage,and the internal resistance during conduction is very low.If the internal resistance of the test voltage is also very small,the tube will burst undoubtedly.
How do the analog electronics divide the field effect transistors according to their output characteristic curve and transfer characteristic curve?
Before distinguishing FETs by output characteristic curve and transfer characteristic curve, we need to understand a concept. FETs are voltage-controlled devices, which are different from bipolar transistors (flow-controlled devices). When FETs work, the gate usually needs only one voltage, and the current is very small or zero. Therefore, in order to achieve this, the junction FETs and MOS have different methods to achieve this effect, resulting in different characteristic curves.
The junction field effect transistor (JFET) uses a reverse diode between the gate and the channel, and applies a reverse voltage on the diode. When the diode works in the opposite direction, the current is very small to achieve the voltage control effect. Therefore, when the junction field effect transistor works, the gate control voltage UG always needs to ensure that the diode works in the opposite direction, that is, N. The gate voltage of channel P is positive and the gate voltage of channel P is negative. As for the polarity of drain current, it can be through N channel, N represents negative, external current flows into D electrode, current direction is positive, P channel current flows out of D electrode, current direction is negative. So, the graph below is a good memory.
Output Curve of Field Effect Transistor (Example Interpretation)
The MOS transistor directly interrupts the insulation between the gate and the channel without any current passing through. Therefore, according to the normal positive voltage control N channel, negative voltage control P channel principle. When working, the N-channel gate voltage is positive and the P-channel gate voltage is negative. The current direction is the same as that of the junction tube. N channel, N represents negative, external current flows into D pole, current direction is positive, P channel current flows out of D pole, current direction is negative. The characteristic curve of the MOS transistor can be determined. As for how to distinguish the enhanced type from the depleted type, we only need to see that the control curve intersects with the Y axis. That is, when UG = 0, the drain current is not zero, that is, the drain current is depleted type. When UG = 0, the drain current is zero, that is, the enhanced type.
According to the transfer characteristic curve of FET, how to judge what kind of channel it is?
First of all, it is simple to judge whether N-type or P-type, as long as the observation curve is above or below the coordinates, the upper part is N-type channel (stipulation); as for the enhanced or exhausted type, it is also simple, the enhanced type is only in 1/4 interval coordinates, while the exhausted type is generally in half coordinates; in addition, about the junction type or the insulated grid type. Look at the curve amplitude, infinitely close to the coordinate axis is the junction, insulated grid curve has a starting point on the coordinate axis, and the curve amplitude is steep.
Field effect transistors (FETs) can be divided into two main types: junction field effect transistors (JFETs) and insulated gate field effect transistors (MOSs) according to the presence or absence of conductive channels.