Chapter 7, Problem 7.15EP

The cascode circuit in Figure 7.65 has parameters $V^{+}=12\text{V}$ , $V^{-}=0$ , $R_1=58.8\text{kΩ}$ , $R_2=33.3\text{kΩ}$ $R_3=7.92\text{kΩ}$ , $R_C=7.5\text{kΩ}$ , $R_S=1\text{kΩ}$ , $R_E=0.5\text{kΩ}$ , and $R_L=2\text{kΩ}$ . The transistor parameters are: $\beta =100$ , $V_{BE}\text{(on)=0}\text{.7V}$ , $V_A=\infty$ , $C_{\pi }=24\text{pF}$ , and $C_{\mu }=3\text{pF}$ . Let $C_L$ be an open circuit. (a) Determine the 3dB frequencies corresponding to the input and output portions of the equivalent circuit. (b) Calculate the small−signal midband voltage gain. (c) Correlate the results from parts (a) and (b) with a computer analysis. (Ans. (a) $f_{H\pi }=7.15\text{MHz}$ , $f_{H\mu }=33.6\text{MHz}$ , (b) $\left|A_{\upsilon }\right|=22.5$ )