The transistor in the amplifier shown below has following parameters: $$${h_{fe}}\, = \,100,\,{h_{ie}}\, = \,2k\Omega ,\,{h_{re}}\, = \,0,$$$ $${h_{oe}}\, = \,0.05\,\,m\Omega .\,\,C$$ is very large.

The output impedance is

Each transistor in the Darlington pair (see Fig. below) has h_fe = 100. The overall h_fe of the composite transistor neglecting the leakage current is

The quiescent collector current I_c, of a transistor is increased by changing resistance. As a result

The OP-AMP shown in fig. below is ideal. $$R\, = \,\sqrt {L/C.} $$ The phase angle between V₀ and V_i at $$\omega = 1/\sqrt {LC} $$ is