In the JFET circuit shown in Fig assume that R₁||R₂ = 1 M$$\Omega $$ and the total stray capacitance at the output to be 20 pF. The JFET used has g_m = 2mA/V, C_gs = 20 pF and C_gd = 2 pF. Determine the upper cut-off frequency of the amplifier.

In the MOSFET amplifier shown in the fig. below, the transistor has $$\mu \,\, = \,\,50,\,\,{r_d}\,\, = \,\,10\,K\Omega ,\,\,{C_{gs}}\,\, = \,\,5\,\,pF,{C_{gd}}\,\, = \,\,1pF\,\,$$ and $${C_{ds}}\,\, = \,\,2\,pF.$$ Draw a small signal equivalent circuit for the amplifier for midband frequencies and calculate its midband voltage gain.