Re: LZ1AQ amp With 2SC3357
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While you are in the S parameters (wish they would expressly state the reference impedance), the first numbers of the S parameter pairs is the magnitude. Second is the angle. If you divide the |S21| by |S12| that is the "K" factor which must be larger than unity for stability. Less than unity is "unstable". For example an NXP BUF520 shows a K of 6.8 at 6 ghz. at 8V/20 ma and around 4000 at 40 mhz. Jim/VEZ ?
On Friday, February 7, 2025 at 05:16:32 PM EST, W0LEV via groups.io <davearea51a@...> wrote:
All of these BFU5xx series from NXP seem to have a good high ft.? However, if you consult the gain vs. frequency, all of them pretty much die out above 1.8 GHz.? NXP does not rate gain or noise figure above 1.8 GHz.? With an ft of 9 GHz on the BFU550, I'd expect FAR BETTER GAIN above 1.8 GHz, but it just isn't there.? Yes, I realize ft is technically the maximum frequency of oscillation or where the silicon can overcome losses to oscillate.? But, why?? Here are some very telling plots from the NXP data sheet for the BFU550: MSG = Maximum Stable gain. |s21|^2 = 10 log [s21]^2 Nothing useful above 1.8 GHz.? NXP rates the "Transition Frequency" measured at 25 mA and 900 MHz at 11 GHz.? OK.? This isn't what I learned long ago and far away in my EE classes. Well, I looked it up online.? The transition frequency is the frequency at which the gain drops to unity.? Therefore that would be the same as the maximum frequency of oscillation.? So........how do they measure 11 GHz when operating at 900 MHz??? Seems the max frequency of oscillation would be far easier to obtain. Dave - W?LEV On Fri, Feb 7, 2025 at 9:37?PM Mike M via <groups=[email protected]> wrote:
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Dave - W?LEV |
James Redding WA9VEZ