Does a p-channel JFET require a positive or negative value for Vgs? And Why?

Question

Does a p-channel JFET require a positive or negative value for Vgs? And Why?

Answer 1

a p channel device is like a PNP transistor, requiring negative voltages for bias of the drain.

For the gate it needs a small positive voltage to get the device to conduct. This is usually achieved by a resistor gate to ground and a resistor between source and ground, which biases the source a few volts negative, the equivalent of biasing the gate a few volts positive.

The JFET consists of a long channel of semiconductor material. This material is doped so that it contains an abundance of positive charge carriers (p-type), or of negative charge carriers (n-type). There is a contact at each end; these are the source and drain. The third control terminal, the gate, surrounds the channel, and is doped opposite to the doping-type of the channel, forming a p-n junction at the interface of the two types of the material. Terminals to connect with the outside are usually made Ohmic.

The operation of a JFET is analogous to a garden hose. The flow of water through a garden hose can be controlled by squeezing it and reducing its cross section; the flow of electric charge through a JFET is controlled by constricting the cross section of the current-carrying channel. It is a device in which the current through the conducting region is controlled by an electric field.