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2SC5551
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The ft of the 2SC5551 is 3.5 GHz.? This should show absolutely no gain slump at 30 MHz.? But,being in the GHz range, it will be far more difficult to "tame".? Good ?W layout techniques will be required. As for the size of the NanoVNA and the 1:1 "balun", yes, the Nano is small enough that the balun is not necessary at HF frequencies so long as short leads are used in the test setup.? I can not use my 8753C for such measurements!! ?? Dave - W?LEV |
¿ªÔÆÌåÓýThe output transformer is now the limiting factor for 30 MHz high end gain. The 2SC5551 is much less susceptible to UHF oscillation than many other such transistors, though some circuits using it still require ferrite beads to tame oscillations. The LZ1AQ circuit does not need them. 73, Steve AA7U On 7/12/2024 2:56 PM, W0LEV via
groups.io wrote:
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On Fri, Jul 12, 2024 at 03:00 PM, Steve Ratzlaff wrote:
The 2SC5551 is much less susceptible to UHF oscillation than many other such transistorsI can support this observation from my own experience with some higher fT Transistors. I believe the lower junction capacitances and feedback capacitances of newer generation bipolar processes are one reason for that. Positive feedback loops due to poor PCB-layout is IMHO in most cases the reason for parasitic oscillation of an amplifier circuit. regards Fred |
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