From: Bruce Griffiths bruce.griffi...@xtra.co.nz
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
Its easy to calculate a lower bound to the amplifier phase noise floor
from the signal level at the output and the amplifier output noise due
to feedback resistors together with the
life speed wrote:
From: Bruce Griffithsbruce.griffi...@xtra.co.nz
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
Its easy to calculate a lower bound to the amplifier phase noise floor
from the signal level at the output and the amplifier output noise due
to feedback resistors
From: Pete Rawson peteraw...@earthlink.net
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
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From: Bruce Griffiths bruce.griffi...@xtra.co.nz
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
(Clay)
The calculation is useful to help eliminate amplifiers that will not
meet the phase noise floor specs.
The amplifiers that remain will then need to be tested/measured
I have been thinking about how to make the measurement. I don't
normally measure OCXO phase noise. I buy them to spec and lock
my synthesizer to them, measuring phase noise at microwave
frequencies using an older Agilent E5500 system with an 8254 (?)
signal generator reference, which is an
Clay,
I'm not sure what the leadless package looks like, so I'll check it out.
The only older leadless packages I can't deal with are BGA and the
leadless ceramic chip carrier. Would you send me a complete P/N
to be sure I'm looking at the right thing?
This would still be a very useful
Message: 6
Date: Fri, 19 Feb 2010 15:17:44 -
From: Garry Thorp gth...@pascall.co.uk
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
Hello Clay,
Joining in this discussion at a rather late stage - have you
considered using 74AC series gates as buffers? They provide
Thank you, but I require a circuit without transformers
for reasons of vibration susceptibility.
Is the problem wires moving relative to eachother within the transformer or
the whole transformer moving relative to the local magnetic field?
Does it help to pot things in epoxy or varnish or
Date: Thu, 18 Feb 2010 15:22:40 +1300
From: Bruce Griffiths bruce.griffi...@xtra.co.nz
Clay
What's the effect of assigning the same label (Vout_2) to the outputs of
both output amplifiers as shown in your circuit schematic?
Bruce
Hi Bruce,
Duplication of the Vout_2 net labels (copy and paste
life speed wrote:
Date: Thu, 18 Feb 2010 15:22:40 +1300
From: Bruce Griffithsbruce.griffi...@xtra.co.nz
Clay
What's the effect of assigning the same label (Vout_2) to the outputs of
both output amplifiers as shown in your circuit schematic?
Bruce
Hi Bruce,
Duplication of the Vout_2 net
-Original Message-
Lastly, my customer, the system designer, would now like to be able to add
a switch function to the
10 MHz distribution. I will have to check and see if switching of bias
current to these two-stage
transistor amp circuits can accomplish this function.
Message: 5
Date: Thu, 18 Feb 2010 11:11:18 -0800
From: Hal Murray hmur...@megapathdsl.net
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
(Clay)
Thank you, but I require a circuit without transformers
for reasons of vibration susceptibility.
Is the problem wires moving
(Clay)
Message: 5
Date: Thu, 18 Feb 2010 11:11:18 -0800
From: Hal Murray hmur...@megapathdsl.net
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
(Clay)
Thank you, but I require a circuit without transformers
for reasons of vibration susceptibility.
Is the problem wires moving
The problem is modulation of the reference signal via relative
movement of the transformer guts. While I understand there are ways
to 'harden' magnetic devices, my application is far too sensitive to
even consider a magnetic approach given the availability of
alternatives. Any spurious
Hi
Vibration modulates lead inductance. That's true even on SMT semiconductors..
It's true big time for leaded parts of the axial persuasion. Weather the amount
of change matters to you is another thing entirely.
If you stick with NPO even for the bypass caps, the piezo stuff is not going to
Hal Murray wrote:
The problem is modulation of the reference signal via relative
movement of the transformer guts. While I understand there are ways
to 'harden' magnetic devices, my application is far too sensitive to
even consider a magnetic approach given the availability of
alternatives.
Message: 5
Date: Thu, 18 Feb 2010 17:13:55 -0500
From: Bob Camp li...@cq.nu
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
(Clay)
To: 'Discussion of precise time and frequency measurement'
time-nuts@febo.com
Message-ID: 13d264786a8a41e781bb4e53c1dd9...@vectron.com
Content
The TI THS3201-EP was looking pretty good for a high speed opamp. But the
input current noise graph doesn't go below 100 KHz and is climbing pretty
steeply at that point.
Clay
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on 10 MHz isolation/distribution
(Clay)
To: 'Discussion of precise time and frequency measurement'
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Hi
Have you looked into any actual data on small rf
Message: 3
Date: Thu, 11 Feb 2010 23:02:30 -0500
From: Bob Camp li...@cq.nu
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
(Clay)
Hi
I suspect your noise spike can be cured by a series R-C to ground from the
junction of Q1 base, Q7 base and all the other stuff. Something
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
(Clay)
Hi
I suspect your noise spike can be cured by a series R-C to ground from the
junction of Q1 base, Q7 base and all the other stuff. Something is going to
have to set a high frequency roll off. With no coils some combo
I seem to not be accomplishing much isolation from output to input, as well as
output to output. Have I fumbled PSPICE somehow? For each simulation, Vac was
set separately, with V1=0.707V at the input, while V6=0V at the output (sim1).
Then V1=0V, and V6=0.01V (sim2).
Hi
There are a few differences between what you are simulating and the schematics
Bruce posted earlier. The collectors of the input stages (q1, q4 and q7) seem
have to come unglued from the bases of the output stages. The 95 ohm / 100 nf
roll off networks seem to have vanished from the
life speed wrote:
I seem to not be accomplishing much isolation from output to input, as well as
output to output. Have I fumbled PSPICE somehow? For each simulation, Vac was
set separately, with V1=0.707V at the input, while V6=0V at the output (sim1).
Then V1=0V, and V6=0.01V (sim2).
The series RC to ground keeps the high frequency impedance seen by Q1
and Q7 low so that the base current noise which increases significantly
as the frequency approaches the ft of these transistors.
However such a series RC network does little to suppress the the rise
due to gain peaking.
A
Hi
Since it's the input stage, it's likely the point most impacted by a higher
flicker noise part. That might make one want to look at alternatives.
Of course, it's not real clear that a super low noise amp is needed in this
case.
Bob
On Feb 12, 2010, at 8:46 PM, Bruce Griffiths wrote:
In the later version the input amplifier has a gain of 2x and the output
amplifiers have unity gain.
Whilst the reverse isolation (and output impedance) can be improved by
using a complementary symmetry emitter follower output stage, one has to
ask at that point is the performance gain worth
Hi
I have no data, but I believe that in the real application, the phase noise
would not be degraded by a good low noise RF op amp / buffer amp. About all you
can do for flicker noise data is to look at what they do supply and make an
guess based on how the noise rolls up over the range they
The only data available seems to be John Ackermann's measurements on the
TADD-1 distribution amp.
Unfortunately the opamp used is now obsolete or about to be.
Most recent discrete designs (not the HP5087 amplifiers) that I have
seen phase noise data for, have significantly lower flicker phase
Hi
There's also the throw everything at it approach.
Use something like common base stages for the input and op amps for the
outputs. Boost the level into the op amps and pad it at the outputs. You might
get what you need. More parts than a pure op amp design, more current. Likely
easier to
One issue with opamps may be the distortion as few of the high frequency
ones have distortion data for more than 2Vpp output.
Its can be little optimistic to scale from this if they plot distortion
vs input (or output level) or give IP2 and IP3 specs.
+10dB in 50 ohms requires 4V pp at the
Message: 1
Date: Thu, 11 Feb 2010 12:42:27 -0500
From: Bob Camp li...@cq.nu
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
amplifier(Clay)
Hi
I really should learn how to read the whole message
Cancel the second request on vibe info.
-
The gotcha
: Bob Camp li...@cq.nu
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
amplifier(Clay)
Hi
I really should learn how to read the whole message
Cancel the second request on vibe info.
-
The gotcha with vibration isolation is that it will stop
life speed wrote:
Message: 1
Date: Thu, 11 Feb 2010 12:42:27 -0500
From: Bob Campli...@cq.nu
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
amplifier(Clay)
Hi
I really should learn how to read the whole message
Cancel the second request on vibe info
Message: 2
Date: Fri, 12 Feb 2010 12:12:29 +1300
From: Bruce Griffiths bruce.griffi...@xtra.co.nz
The output (collectors of Q5, Q6 emitter of Q4) of the input amplifier
sets the dc voltage at the inputs ( Q1 base, Q7 base respectively) of
the output amplifiers.
The circuit consists of a unity
life speed wrote:
Message: 2
Date: Fri, 12 Feb 2010 12:12:29 +1300
From: Bruce Griffithsbruce.griffi...@xtra.co.nz
The output (collectors of Q5, Q6 emitter of Q4) of the input amplifier
sets the dc voltage at the inputs ( Q1 base, Q7 base respectively) of
the output amplifiers.
The circuit
Hi
I suspect your noise spike can be cured by a series R-C to ground from the
junction of Q1 base, Q7 base and all the other stuff. Something is going to
have to set a high frequency roll off. With no coils some combo of R and C is
going to have to do it.
You might also try returning all of
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