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broadband monolithic amplifier

K

kris

Jan 1, 1970
0
Hi All,

Good Morning. I am using a broadband monlithic amplifier (ERA-3SM
from minicircuits) in a transmitter circuit for broadband
applications.
A 44MHz signal is the input to this amplifier, the measured power
levels at the input and the output are 1 dBmV and 34dBmV
respectively.I am looking for a better amplifier which can provide
around 40dBmV as output when the input is around 1dBmV, any help or
suggestions from anyone will be greatly appreciated.

Thanks,
kris
 
J

John Woodgate

Jan 1, 1970
0
Hi All,

Good Morning. I am using a broadband monlithic amplifier (ERA-3SM
from minicircuits) in a transmitter circuit for broadband
applications.
A 44MHz signal is the input to this amplifier, the measured power
levels at the input and the output are 1 dBmV and 34dBmV
respectively.I am looking for a better amplifier which can provide
around 40dBmV as output when the input is around 1dBmV, any help or
suggestions from anyone will be greatly appreciated.
I am suspicious of your figures in 'dBmV', which is NOT a measure of
power. 1 dBmV is 1.12 mV; is that what you mean? 34 dBmV is 50 mV and 40
dB mV is 100 mV; again, is that what you mean?

Or do you mean '1 dBm' (1.26mW), '34 dBm' (2500 mW) and 40 dBm (10 W)?
It makes a LOT of difference!
 
J

John Larkin

Jan 1, 1970
0
I am suspicious of your figures in 'dBmV', which is NOT a measure of
power. 1 dBmV is 1.12 mV; is that what you mean? 34 dBmV is 50 mV and 40
dB mV is 100 mV; again, is that what you mean?

Or do you mean '1 dBm' (1.26mW), '34 dBm' (2500 mW) and 40 dBm (10 W)?
It makes a LOT of difference!

"dBmv" just means dB measured with a 1 mv reference being uses as 0
dB. It's the same idea as dBv, where 0 volts is 0 dB.

What's actually suspicious here is getting 34 dB gain from an ERA-3.

John
 
K

kris

Jan 1, 1970
0
1 dBmV is dB referenced to one millivolt across 75 ohms.
0 dBm = 48.75 dBmV (for more info
http://www.scte.org/chapters/newengland/reference/dbm_to_ dbmv_Conversion.htm)
I indeed observed the 34 dBmV output power for the ERA-3SM when the
input was around 1dBmV,it was quite repeatable.The specification sheet
mentions around 23 dB gain over 0.1GHz range, the frequency I was
using was 44MHz.I am not sure if the gain mentioned in the
specification sheet is power gain (23dB).
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.

Thanks,
Kris.
 
M

Mac

Jan 1, 1970
0
I am suspicious of your figures in 'dBmV', which is NOT a measure of
power. 1 dBmV is 1.12 mV; is that what you mean? 34 dBmV is 50 mV and 40
dB mV is 100 mV; again, is that what you mean?

If that is what the OP means, an op-amp second stage will work nicely, and
since the noise figure is set by the first amp, it should have no effect
on the SNR.
Or do you mean '1 dBm' (1.26mW), '34 dBm' (2500 mW) and 40 dBm (10 W)?
It makes a LOT of difference!

Obviously, if the OP needs 10 Watts out, that is going to require a real
RF amplifier.

Mac
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that John Larkin <jjlarkin@highSNIPland
THIStechPLEASEnology.com> wrote (in <k1rg00hv0cgoln1mqu57ncrhkt20hlmc32@
4ax.com>) about 'broadband monolithic amplifier', on Fri, 16 Jan 2004:
"dBmv" just means dB measured with a 1 mv reference being uses as 0
dB. It's the same idea as dBv, where 0 volts is 0 dB.

I'm aware of that. I'd better be, since I chaired the group that wrote
the Audio Engineering Society publication AES-R2-1998 on the subject.

My question, which I would have thought was obvious from my post, is
whether the OP meant dBmV (an unusual measure in RF circles) or dBm (the
normal measure, which SHOULD actually be written dB(mW). See IEC
60027-3.)
What's actually suspicious here is getting 34 dB gain from an ERA-3.

Yes, well, confusion over the use of decibels can produce results like
that.
 
J

John Woodgate

Jan 1, 1970
0
1 dBmV is dB referenced to one millivolt across 75 ohms.

No. 1 dBmV is 1 dB above 1 mV; the impedance is not defined. See IEC
60027-3.

But are you really putting in 1 dBmV = 1.122 mV? Or is it actually 1 mV
= 0 dBmV?

It's simply wrong. It's taken stuff from elsewhere and reproduced it
without understanding. It also attributes the volt to Voltaire
(bizarre!) instead of to Alessandro Volta!
I indeed observed the 34 dBmV output power

dBmV is a VOLTAGE LEVEL, NOT a power. Power is measured in (milli)watts,
and power level in dBm, which should really be written dB(mW), or dBW.
for the ERA-3SM when the
input was around 1dBmV,it was quite repeatable.The specification sheet
mentions around 23 dB gain over 0.1GHz range, the frequency I was
using was 44MHz.I am not sure if the gain mentioned in the
specification sheet is power gain (23dB).

It doesn't matter, voltage gain and power gain are identical IF the
impedances at the input and output are the same.

But there is something wrong if the gain spec is 23 dB and you measure
33 dB. Have you terminated the output in 50 ohms or whatever the data
sheet requires? Are you measuring 1.122 mV EMF (i.e. the voltage before
the source impedance: some signal generators are calibrated in EMF on
their 'mV' attenuator scales) at the input or 1.122 mV across the input
terminals? I ask, because if you have it wrong at both ends, you would
'measure' 1 + 23 + 12 = 36 dBmV approximately, quite close to your 34
dBmV.
 
M

maxfoo

Jan 1, 1970
0
1 dBmV is dB referenced to one millivolt across 75 ohms.
0 dBm = 48.75 dBmV (for more info
http://www.scte.org/chapters/newengland/reference/dbm_to_ dbmv_Conversion.htm)
I indeed observed the 34 dBmV output power for the ERA-3SM when the
input was around 1dBmV,it was quite repeatable.The specification sheet
mentions around 23 dB gain over 0.1GHz range, the frequency I was
using was 44MHz.I am not sure if the gain mentioned in the
specification sheet is power gain (23dB).
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.

Thanks,
Kris.


try using a larger value inductor on the bias line 500-1000nH, you'll get a bit
more gain.



Remove "HeadFromButt", before replying by email.
 
J

John Todd

Jan 1, 1970
0
I am suspicious of your figures in 'dBmV', which is NOT a measure of
power. 1 dBmV is 1.12 mV; is that what you mean? 34 dBmV is 50 mV and 40
dB mV is 100 mV; again, is that what you mean?

Or do you mean '1 dBm' (1.26mW), '34 dBm' (2500 mW) and 40 dBm (10 W)?
It makes a LOT of difference!

dBmV is the old cable television standard for line measurements,
and assumes 75 ohm line impedance, AFAIK.
 
K

kris

Jan 1, 1970
0
I'm aware of that. I'd better be, since I chaired the group that wrote
the Audio Engineering Society publication AES-R2-1998 on the subject.

John, Pardon my ignorance, I am just a recent college grad trying to
get the work done quickly in the work place, thanks for providing the
insight about dBmV.
I am taking the measurements using a digital signal analyzer(from
hukk engineering) which is showing the values in dBmV. i.e it displays
as "30dBmV" etc. on its screen.

thanks again,

kris
 
J

John Woodgate

Jan 1, 1970
0
John, Pardon my ignorance,

I wasn't trying to put you down.
I am just a recent college grad trying to
get the work done quickly in the work place, thanks for providing the
insight about dBmV.
I am taking the measurements using a digital signal analyzer(from
hukk engineering) which is showing the values in dBmV. i.e it displays
as "30dBmV" etc. on its screen.

H'mm; and does it show '1 dBmV' as well? I don't know what that
instrument is, but it doesn't seem like one that's normally used for RF
measurements. Do you know its input impedance?
 
A

Active8

Jan 1, 1970
0
I read in sci.electronics.design that John Larkin <jjlarkin@highSNIPland
THIStechPLEASEnology.com> wrote (in <k1rg00hv0cgoln1mqu57ncrhkt20hlmc32@
4ax.com>) about 'broadband monolithic amplifier', on Fri, 16 Jan 2004:


I'm aware of that. I'd better be, since I chaired the group that wrote
the Audio Engineering Society publication AES-R2-1998 on the subject.

My question, which I would have thought was obvious from my post, is
whether the OP meant dBmV (an unusual measure in RF circles)

Tell that to Scientific Atlanta, General Intrumaents, Magnavox, and
all the other broadband CATV amp mfgs.
or dBm (the
normal measure, which SHOULD actually be written dB(mW). See IEC
60027-3.)

Yes, well, confusion over the use of decibels can produce results like
that.

What? 1 dB gain on 1dBmV is 2dBmV and 1dB gain on 1dBm is 2dBm. It
doesn't matter what the reference is as long as you're comparing
apples to apples. The difference between output and input is Gain
in dB.
 
A

Active8

Jan 1, 1970
0
On 19 Jan 2004 08:52:35 -0800, [email protected] said...
John, Pardon my ignorance, I am just a recent college grad trying to
get the work done quickly in the work place, thanks for providing the
insight about dBmV.
I am taking the measurements using a digital signal analyzer(from
hukk engineering) which is showing the values in dBmV. i.e it displays
as "30dBmV" etc. on its screen.

That's what my SLM uses, but I've seen units that can be set for
dBuV. All this talk about dBm being "normal" or "common" in RF
circles most likely stems from the use of specrtum analysers and
power meters. Noise floor and noise levels are commonly expressed
in dBm also. Just remember to be careful comparing and reading
specs and all that.
 
A

Active8

Jan 1, 1970
0
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.
Thanks,
Kris.
<snip>
 
A

Active8

Jan 1, 1970
0
If that is what the OP means, an op-amp second stage will work nicely, and
since the noise figure is set by the first amp, it should have no effect
on the SNR.


Obviously, if the OP needs 10 Watts out, that is going to require a real
RF amplifier.

Mac
Yeah. Forget my idea of piggybacking another MMIC on there in
cascade :( I gotta remember to think that crap through. :)
 
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