A Darlington stage is shown in the figure, if the transconductance of q₁ is g_m1 and q₂ is g_m2, then the overall transconductance
$$g\matrix{ c \cr m \cr } \left[ { \buildrel \Delta \over = {{{i_c}^c} \over {{v_{be}}^c}}} \right]$$ is given by

An npn transistor has a beta cut-off frequency $${f_\beta }$$ of 1MHz and Common Emitter short circuit low frequency current gain $${\beta _o}$$ of 200. The unity gain frequency $${f_T}$$ and the alpha cut-off frequency $${f_\alpha }$$ respectively are

In the circuit shown in Fig. is a finite gain amplifier with a gain of K, a very large input impedance, and a very low output impedance. The input impedance of the feedback amplifier with the feedback impedance Z conducted as shown will be

A common-emitter amplifier with an external capacitor C_C connected across the base and the collector of the transistor is shown in Fig.

Transistor data g_m = 5mA/V, $${r_\pi }\, = \,200K\Omega, $$ $${C_\pi }\, = \,1.5$$ pF and $$C\mu \, = \,0.5$$ pF determine the upper cutoff frequency f_H of the amplifier