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1. Design
The first power amp has 2 stages(MGF0904, MGF-0905) and provides 4W output power with 18dB of gain (Fig. 1/3). The second power amp has 3 stages and provides 8W output power with more than 20dB of gain (Fig. 2). It has been developed by JA2QGE. The circuit diagram of the 3-stage amp is like the 2-stage with one stage added. Both are constructed on G-10 epoxy material. The bias circuit can be seen in Fig. 4 and is standard.
Figure 1: PCB of 4W Amp
Figure 2: PCB of 8W Amp
Figure 3: Circuit of 4W Amplifier
Figure 4: Bias Circuit
2. Results
| Item | 2-Stage | 3-Stage |
|---|---|---|
| Gain/dB | 18 | >20 |
| P ldB/W | 4W @ 9V | 8W @ 10V |
| BW/MHz | 550 | |
| Ids/A | 0.2/0.8 | 0.2/0.8/1.34 |
JE1AAH, Toshihiko Takamizawa.