**Fet Tuned Amplifier – Circuit Diagram and Frequency Response:**

Figure 18.11(a) depicts the circuit of an FET tuned amplifier. It uses a first-order JFET model for the 2N 5484 [I_{DSS} = 2.41 mA, V_{P} = -1.2 V]. Thus,

Drain current,

and

when gate voltage is 4.29 V

Solving for the quiescent bias values I_{D} = 1.19 mA and V_{GS} = – 0.35 V.

A SPICE computation provides V_{GS} = – 0.4 V and I_{D} = 1.24 mA. The noteworthy point is that the first order does not allow for **channel length modulation**.

Small signal model for operation at resonance is shown in Fig. 18.11(b). Using the computed bias current and voltage values the transconductance g_{m} is 2.84 mA/V. The voltage gain at resonance then is 92.3 (39.3 dB).

The calculated resonant frequency is 50.35 kHz. The calculated Q is approximately 104 and the 3 dB bandwidth therefore is estimated to be 484 Hz Pspice is used to provide the numerical analysis of the amplifier performance plotted below [Fig. 18.11 (c)].