On 16 Jan 2004 22:55:38 -0800,
[email protected] said...
1 dBmV is dB referenced to one millivolt across 75 ohms.
the impedance is not specified for the use or non-use of voltage
references. You just have to make sure that when you use dBmV that
you don't compare numbers from different impedance levels.
And I might have guessed your above statement was based on
something out of the cable world. If I had a dime for every
assumption about electronics that came from the cable world, I'd be
rich.
I indeed observed the 34 dBmV output power for the ERA-3SM when the
input was around 1dBmV,it was quite repeatable.
I haven't perused the MC designer's guide in a while, but I don't
recall any 33dB gain devices. I could be wrong.
The specification sheet
mentions around 23 dB gain over 0.1GHz range,
Then 1dBmv in should give 24dBmV out. Even the cable world would
agree with that. Remember logs of products add and logs of ratios
subtract?
the frequency I was
using was 44MHz.I am not sure if the gain mentioned in the
specification sheet is power gain (23dB).
a dB is a dB is a dB is a ratio. If you're working with voltage
referenced dB's, you can't calculate Gain with subtraction unless
the input and output impedances are the same. That's another good
reason why power referenced dB's are so common. Chances of
impedance levels being the same from stage to stage in a receiver,
for example, are slim. 75 ohm systems are another story. They're
designed that way for purposes of modularity.
John, thanks for your suggestion. My problem is this ERA amplifier is
on a PCB, I have to somehow increase the gain by finding something
which can be replaced in the same footprint of this ERA amplifier.
Ouch! I was going to suggest a cascade... but... you could
piggyback another MMIC on top of the exsisting one maybe.
Now I'm seeing a possible reason why your measurements may be
wrong. MC MMIC's are 50 ohm devices and you're measuring with a 75
ohm meter. Should read high.
<snip>