MESFET Distributed Amplifier Design Guidelines

Abstract

In thk paper, the anafysis of GGAS MESFET distributed amplifiers and a systematic approach to their design are presented. The analysis focuses on fundamental design considerations and afso establishes the maximum gain-bandwidth product of the amplifier. The design approach presented enables one to examine the tradeoffs between the variables, such as the device, the number of devices, and the impedances and cutoff freqnency of the lines, and arrive at a design which gives the desired frequency response. Excellent agreement is shown when the theoretically predicted response of a typicaf amplifier is compared with computer-aided anafysis results, and good agreement is shown with previously published experimental results. 1.

Dual Fed Distributed Amplifier With Controlled Termination Adjustment

“…As the gain is made close to unity, it becomes inefficient to cascade amplifier stages. On the other hand, combining the outputs from a number of active devices in parallel increases the output power without improvement of the gain-bandwidth product [12]. The basis of the distributed amplification is to superimpose constructively the output currents from a number of devices, refer to Fig.…”

“…The basis of the distributed amplification is to superimpose constructively the output currents from a number of devices, refer to Fig. 1, while avoiding the sum of the shunt capacitances [12].…”

“…Each transistor injects a current of g m v gs , where g m and v gs are transconductance and gate-source voltage, respectively. Since the drain of each transistor is loaded by the same impedance Z π in both directions, hence half of this current travels to the left and half to the right [12], as illustrated in Fig. 2.…”

“…Applying the superposition theorem to the network shown in Fig. 2, the current towards drain termination [12], I R d can be derived as…”

“…The network is assumed to be lossless. Similarly, applying the superposition theorem, the current towards dummy termination I L d [12] is derived as…”