In a series regulated power supply circuit, the voltage gain A_v of the ‘pass’ transistor satisfies the condition:

In the circuit of fig. Determine the resistance R_o seen by the output terminals, ignore the effects of R₁ and R₂.

The $${f_T}$$ of a BJT is related to its $${g_{m,}}\,\,{C_\pi }$$ and $${C_\mu }$$ as follows

In the MOSFET amplifier of the figure the signal output V₁ and V₂ obey the relationship