[time-nuts] Distribution amplifier, v2 simulation+design

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Dec 27 14:15:32 EST 2015


You could use something like an LT3042 for the voltage regulator.The 1/f noise corner can be set with an external cap.It has relatively high PSRR up to 2MHz or so.However it has a maximum output of 200mA.One could use 2 or more if required.
Bruce
 

    On Monday, 28 December 2015 8:00 AM, Anders Wallin <anders.e.e.wallin at gmail.com> wrote:
 

 Hi all,
Based on the response to my distribution amplifier prototype&measurements I
ran a few SPICE simulations with the old AD8055 design and an improved
design.

The changes are:
- better op-amp
- improved DC-bias "T" circuit
- lower resistance values (esp. gain-setting resistors)

results & discussion in my blog:
http://www.anderswallin.net/2015/12/frequency-distribution-amplifier-v2-simulations/

The simulations would indicate a 12 to 13 dB improvement in noise floor is
possible. I could not find a good ADA4899-1 spice model. One has realistic
AC gain response but unrealistic 1/f noise. The other model I found has a
realistic 1/f noise but infinite AC gain bandwidth :(

again suggestions are welcome, I'll probably order boards and parts for the
next prototype in a few days.

I will look at Bruce's suggestion for the BNX002 (SMD equivalent
available?) on the powersupply. There is already a common-mode choke (TDK
ZJYS) and an NFE61P before the regulator, as well as ferrites before the
bypass-caps and vcc-pin of each output amplifier.

thanks!
Anders
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