考慮如右圖N-通道MOSFET等效電路，若忽略rs、rd、ro、Cds及汲極連結到訊號地，kn(W/L)=0.4 mA/V²，VT=1 V，λ=0，Cgd=0.04 pF，Cgs=0.2 pF，給定偏壓VGS=3 V，求單位電流增益的頻率(unity-gain frequency)fT？

正確計算：gm = k'n(W/L)×(VGS−VT) = 0.4×10⁻³×(3−1) = 0.8 mA/V；Cgs+Cgd = 0.2+0.04 = 0.24 pF；fT = 0.8×10⁻³ / (2π×0.24×10⁻¹²) = 0.8/(1.5079×10⁻⁹) ≈ 530 MHz。