SITUATION:

A single stage FET power amplifier needs to be analyzed so that parameter values and specifications may be established; in addition the FET circuit may have an interchangeable op-amp as a preamplifier for various input signal conditions.

REQUIREMENTS:

An n-channel junction FET power amplifier circuit has the drain characteristic curves as shown. The FET circuit eventually will be driven by an op-amp acting as preamplifier for various signal sources. The FET has a maximum drain voltage upper limit of 16 volts. Assume the operating quiescent current, I _D, for the load line is 22 mA and any operation is at mid-band frequencies.

The following information is needed:

1. V _DS and R _L ? for maximum possible output signal excursion.

2. The transformer turns ratio n for an R _L= 8 ? for the R _L ?(as found in 1).

3. Graphically determine the approximate power output when v _gs = 0.5 sin ?t volts.

4. The percentage of second-harmonic distortion for i _D for the same signal as in (3).

5. With the op-amp connected and with a V ₁= 35 mV (rms), determine the value of R ₁ to produce the signal in (3).

Solution

1. 
   

   

2. 
   

   

3. From a load line plot for a v _gs of 0.5V on...