It is required to design a tuned amplifier of the type shown in Fig. 17.42, having f0 = 1 MHz, 3-dB bandwidth = 10 kHz, and center-frequency gain = –10 V/V. The FET available has at the bias point gm = 5 mA/V and ro = 10 kΩ. The output capacitance is negligibly small. Determine the values of RL, CL

Question

It is required to design a tuned amplifier of the type shown in Fig. 17.42, having f₀ = 1 MHz, 3-dB bandwidth = 10 kHz, and center-frequency gain = –10 V/V. The FET available has at the bias point g_m = 5 mA/V and r_o = 10 kΩ. The output capacitance is negligibly small. Determine the values of R_L, C_L, and L.

Accepted Answer

Center-frequency gain = –10 = –5 R. Thus R = 2 kΩ. Since R = R_L|| r_o, then R_L = 2.5 kΩ.

[latex]B = 2π × 10^{4} = \frac{1}{CR}[/latex]

Thus

[latex]C = \frac{1}{2π × 10^{4} × 2 × 10^{3}} = 7958 pF[/latex]

Since [latex]ω_{0} = 2π × 10^{6} = 1 / \sqrt{LC}[/latex], we obtain

[latex]L = \frac{1}{4π^{2} × 10^{12} × 7958 × 10^{−12}} = 3.18 μH[/latex]

Question 17.5: It is required to design a tuned amplifier of the type shown...

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