A bipolar junction transistor amplifier circuit is shown in the figure. Assume that the current source I_bias is ideal, and the transistor has very large$$\beta ,\,\,{r_{b\,\,}} = \,\,0,$$ and the $${r_0}\, \to \,\infty $$.

Determine the ac small-signal mid-band and voltage gain $$\left( {{V_o}/{V_s}} \right),$$ input resistance (R₁, and output resistance (R₀) of the circuit. Assume $${V_{T\,\,}} = \,\,26\,mV.$$

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

In the cascade amplifier circuit shown below, determine the values of R₁, R₂ and R_L. Such that the quiescent current through the transistors is 1mA and the collector voltage V_c1 = 3V, and V_c2 = 6V. Tke V_BE = 0.7V, Transistor $$\beta $$ to be hifgh and base currents to be negligible.

The transistor in the circuit shown in the figure. is so biased (dc biasing N/W is not shown) that the dc collector current I_C = 1mA. Supply is V_CC = 5V.

The N/W components have following values, R_C = 2$$k\Omega $$,
R_S = $$1.4k\Omega $$,
R_E = $$100\Omega $$.

The transistor has specifications, $$\beta \,\, = \,\,100$$
and base spreading resistance $${r_{bb\,}}^1\, = \,100\Omega $$

$$Assume\,\,{{KT} \over q}\,\, = \,\,25\,mV$$

Evaluate input resistance R_i for two cases. At a frequency of 10 kHz

(a)C_E, the bypass capacitor across R_E is 25 $$\mu F$$
(b)The bypass capacitor C_E is removed leaving R_E unbypassed.