Small Signal Model - SubThreshold.com

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Memeber of: Equations

Parameters

g_m: Gain factor for v_gs. Or the change in drain current (i_D) at a given Q point $g_m = \frac{\del i_D}{\del v_{GS}} = \frac{\kapp}{U_T} I_D = I_S \frac{W}L \frac{ \kappa }{U_T} exp{ \frac{ \kappa V_{GS}}{U_T} }$
g_d: Channel Conductance - Small signal drain to source admittance. Or the change in drain to source voltage (V_DS) at a given Q point $g_{d} = \frac{\del I_D}{\del V_{D}} = I_S \frac{W}L exp{ \frac{ \kappa V_{GS}}{U_T} } \frac1{U_T} exp{ \frac{ - V_{D}}{U_T} } \approx \frac{I_D}{U_T} exp{ \frac{ V_{S}}{U_T} } exp{ \frac{ - V_{D}}{U_T} }$
g_s: Body effect gain factor for v_s. Or the change in drain current (i_D) at a given Q point $g_s = \frac{\del i_D}{\del v_{SB}} = I_S \frac{W}L \frac1{U_T} exp{ \frac{ \kappa V_{GB}}{U_T} } exp{ \frac{ -V_{SB}}{U_T} }$