In a CS amplifier, such as that in Fig. 10.3(a), the resistance of the source Rsig = 100

Chapter 10, Problem 10.31

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In a CS amplifier, such as that in Fig. 10.3(a), the resistance of the source \(R_{\text {sig }}=100 \ \mathrm{k} \Omega \text {, }\), amplifier input resistance (which is due to the biasing network) \(R_{\mathrm{in}}=100 \ \mathrm{k} \Omega, \quad C_{g s}=1 \ \mathrm{pF}, \quad C_{g d}=0.2 \ \mathrm{pF}, \quad g_{m}=3 \mathrm{~mA} / \mathrm{V}, r_{o}=50 \mathrm{k} \Omega, R_{D}=8 \mathrm{k} \Omega\), and \(R_{L}=10 \ \mathrm{k} \Omega\). Determine the expected 3-dB cutoff frequency \(f_{H}\) and the midband gain. In evaluating ways to double \(f_{H}\), a designer considers the alternatives of changing either \(R_L\) or \(R_{\mathrm{in}}\). To raise \(f_{H}\) as described, what separate change in each would be required? What midband voltage gain results in each case?