Main characteristic parameters of field-effect transistors

1. Pinch off voltage Up

Under the condition that UDS is a fixed value, when ID equals a small current value (a few microamperes), the bias voltage UGS applied to the gate is the pinch off voltage. It is suitable for junction field-effect transistors and depletion type insulated gate field-effect transistors.
2. Turn on voltage UT

Under the condition of a fixed UDS value, the UGS that forms a conductive channel between the S and D poles is the turn-on voltage. It is only applicable to enhanced insulated gate field-effect transistors.
3. Saturation current IDSS 

Under the condition of UDS=0, the channel current when the voltage applied between the drain and source is greater than the pinch off voltage is called saturation current, which is suitable for depletion type insulated gate field-effect transistors.

4. DC input resistor RGS
The ratio of the voltage Ucs applied to the input terminal of the field-effect transistor (i.e. between the gate and source) to the gate current flowing through it is called the DC input resistance. The DC input resistance of insulated gate field-effect transistors is more than two orders of magnitude higher than that of junction field-effect transistors. The DC input resistance of junction field-effect transistor is 1 X 10 8 Ω, while the DC input resistance of insulated gate field-effect transistor is above 1 X 10 12 Ω.

5. Leakage source breakdown voltage BVDS

The UDS value that causes a significant increase in ID during the process of increasing leakage and voltage is called the leakage source breakdown voltage. BVDS has determined the operating voltage of field-effect transistors.

6. Gate source breakdown voltage BVGS

For junction field-effect transistors, the UGS value at which the reverse saturation current begins to increase sharply is the gate and breakdown voltage. For insulated gate field-effect transistors, it is the voltage that causes the breakdown of the SiO2 insulation layer.