DC Parameters
Saturation Drain Current (IDSS): Defined as the drain current when the gate-source voltage is zero, but the drain-source voltage is greater than the pinch-off voltage.
Pinch-off Voltage (UP): Defined as the UGS required to reduce ID to a very small current when UDS is constant.
Take-off Voltage (UT): Defined as the UGS required to bring ID to a certain value when UDS is constant.
AC Parameters
AC parameters can be divided into two categories: output resistance and low-frequency transconductance. Output resistance is typically between tens and hundreds of kilohms, while low-frequency transconductance is generally in the range of a few tenths to a few millisieverts, with some reaching 100 ms or even higher.
Low-frequency transconductance (gm): Describes the control effect of the gate-source voltage on the drain current.
Inter-electrode Capacitance: The capacitance between the three electrodes of a MOSFET. A smaller value indicates better transistor performance.
Limiting Parameters
① Maximum drain current: The upper limit of the allowable drain current during normal operation of the transistor.
② Maximum power dissipation: The power in the transistor, limited by the transistor's maximum operating temperature.
③ Maximum drain-source voltage: The voltage at which avalanche breakdown occurs, when the drain current begins to rise sharply.
④ Maximum gate-source voltage: The voltage at which the reverse current between the gate and source begins to increase sharply.
In addition to the above parameters, there are other parameters such as inter-electrode capacitance and high-frequency parameters.
Drain and source breakdown voltage: When the drain current rises sharply, the UDS (Upper Demand) occurs during avalanche breakdown.
Gate breakdown voltage: During normal operation of a junction field-effect transistor (JFET), the PN junction between the gate and source is reverse-biased. If the current is too high, breakdown will occur.
The main parameters to focus on during use are:
1. IDSS-Saturation drain-source current. This refers to the drain-source current in a junction or depletion-type insulated-gate field-effect transistor when the gate voltage UGS = 0.
2. UP-Pinch-off voltage. 3. **UT-Take-on Voltage:** The gate voltage at which the drain-source junction is just turned off in a junction-type or depletion-type insulated-gate field-effect transistor (IGFET).
4. gM-Transconductance: Represents the control capability of the gate-source voltage UGS over the drain current ID, i.e., the ratio of the change in drain current ID to the change in gate-source voltage UGS. gM is an important parameter for measuring the amplification capability of an IGFET.
5. BUDS-Drain-Source Breakdown Voltage: The maximum drain-source voltage that the IGFET can withstand under normal operation when the gate-source voltage UGS is constant. This is a limiting parameter; the operating voltage applied to the IGFET must be less than BUDS.
6.PDSM-Maximum Power Dissipation:Also a limiting parameter, it refers to the maximum allowable drain-source power dissipation without degrading the performance of the IGFET. In use, the actual power consumption of the IGFET should be less than PDSM with a certain margin. 7. **IDSM-Maximum Drain-Source Current:** IDSM is a limiting parameter that refers to the maximum current allowed to pass between the drain and source of a field-effect transistor (FET) during normal operation. The operating current of the FET should not exceed IDSM.
