Q.Explain the terms I_D, I_DSS, g_m, g_mo and μ .

These five symbols name the key currents and small-signal parameters used to describe a JFET. …

[!TLDR]

$I_D$ is the drain current; $I_{DSS}$ is its maximum value at $V_{GS}=0$; $g_m$ is the transconductance; $g_{mo}$ is $g_m$ at zero bias; $\mu$ is the amplification factor.

$I_D$ (drain current): the current that flows through the channel from drain to source when a suitable drain-to-source voltage is applied; it is the output current controlled by the gate voltage.

$I_{DSS}$ (drain-to-source saturation current): the maximum drain current that flows in the saturation region when the gate-to-source voltage is zero $(V_{GS}=0)$. It is a fixed characteristic value of a given JFET.

$g_m$ (transconductance): the ratio of a small change in drain current to the corresponding small change in gate-to-source voltage at constant $V_{DS}$,

expressed in siemen (S); it measures the control of the gate over the drain current.

$g_{mo}$: the value of the transconductance when the gate-to-source voltage is zero, i.e. the maximum transconductance. It is related to the other parameters by $g_{mo} = -\dfrac{2 I_{DSS}}{V_P}$, and $g_m = g_{mo}\left(1 - \dfrac{V_{GS}}{V_P}\right)$. …