One could possibly use another transistor pair in front of this one.
For lower rate signals, it is a great "finalizer" solution to a
step-wise increase in bandwidth and slew-rate.
Cheers,
Magnus
On 07/29/2014 02:54 PM, br...@ko4bb.com wrote:
I merely used the evaluation board which has a capacitively coupled input.
The transformer coupled input circuit using a 1:4 (turns ratio) step up
transformer
as depicted on the datasheet should reduce the PN floor by at least 3dB for
10MHz input.
Bruce
On July 29, 2014 at 7:30 AM "David C. Partridge"
<david.partri...@perdrix.co.uk> wrote:
Bruce,
Thank you, that was very useful information. If I ever do a re-spin of the
divider I will likely use the LTC6957-3 or -4 instead of the ADCMP600 (I
would need interest for at least 40 boards to be able to do this at anything
like an economic price).
Will you be putting the full details of the circuit you used up on Didier's
web site? Did you use a transformer based circuit similar to Design Note
514 or just an input capacitor?
Regards,
David Partridge
-----Original Message-----
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of br...@ko4bb.com
Sent: 29 July 2014 12:00
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Sine to square wave converter Phase Noise
Sorry, I meant the LTC6957-4 of course._SELA = l FILTA = L FILTB = H ie an
input stage BW of 160MHz as recommended for a 10MHz + 10dBm input.
Input for the HX4210 was +14dBm.
Comparator was that used in David Partridge's programmable divider (includes
the
74AC04 buffers).
Bruce
On July 29, 2014 at 5:37 AM Magnus Danielson
<mag...@rubidium.dyndns.org>
wrote:
You alternate LTC7957-4 and LTC6957-4 and it is only the later that
exists.
The LTC6957-4 has a single-stage amplifier stage input, with somewhat
programmable bandwidth. I assume you used the 50 MHz BW setting.
Cheers,
Magnus
On 07/29/2014 10:55 AM, br...@ko4bb.com wrote:
Recently I have been comparing the phase noise of the HOlzworth
HX4210 and the LTC7957-4.
I have found that the performance of these devices is comparable
with a 10MHz sinewave input with a PN noise floor below -160dBc/Hz.
For offsets below 100Hz the LTC6957-4 is quieter and for offsets
below 50Hz or so is lower than that of my measurement setup.
I merely mounted the LTC evaluation board in a diecast metal box to
reduce the effect of air currents on the LTC7957-4 and used an ultra
low noise 3.3V power supply (Abracon) to minimise the power supply
contribution to the measured phase noise.
Achieving a phase noise performance equal to that on the datasheet
was relatively easy.
In fact for low offsets the phase noise is lower than that shown on
the datasheet.
I've also measured the phase noise of a comparator based sine to
CMOS converter and its PN floor is about 20dB higher than that of
the LTC6957.
On completion of measurements PN plots for the various sine to
square conveters tested will be added to the web pages I maintain on
Didiers site..
Bruce
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