Based on carrier number fluctuation model, $1/f$ noise is analyzed for organic thin-film transistors (TFTs) at low drain voltage. The carrier mobility is gate-voltage-dependent, and is described by a power-law function. The mobility power-law parameter $\alpha $ determines the relationship between drain current noise power spectral density (PSD) $S_{I_{\mathrm {D}\mathrm {S}}}$ and drain current $I_{\mathrm {D}\mathrm {S}}$, and it is found that $S_{I_{\mathrm {D}\mathrm {S}}}/I_{\mathrm {D}\mathrm {S}}^{2} \propto I_{\mathrm {D}\mathrm {S}}^{-...
