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Grounded-Gate dual-JFET
VHF Masthead
Amplifier
Original design sourced from Elektor BOOK 75; page 56
Claims Gain of
10~20db with a NF of 1~2db
Quote: A secondary advantage of the common gate amplifier is that the
difference in matching for minimum noise or maximum gain is much less that the
common source cct (and in some cases is even negligible)
RADIO reception
requires matching to minimum noise,
TV reception requires matching to minimum
power gain to eliminate cable reflection (picture ghosts). |
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| Configuration |
Gain |
Input Z |
Output Z |
F/B capacity |
Conclusion |
| Common Source |
Higher |
1 ~ 20KΩ @100MHz (higher) |
Similar to I/P |
1.0 ~ 10.0 pF |
Can be unstable ! |
| Common Gate |
Lower |
1/slope (mA/V) ±20%
~ 200Ω
(lower) |
Similar to I/P |
0.01 ~ 0.1 pF |
Reliable & stable |
Vero board layout and prototype.
Remote power supply and tuning box
Single Coax cable for
signal/supply/tuning
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