The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: John Woodgate
Subject: Re: antilog amplifier
Date: Thu, 28 Nov 2002 06:53:04 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Thu, 28 Nov 2002 09:27:33 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Kevin White
wrote (in )
about 'antilog amplifier', on Thu, 28 Nov 2002:
>"Phil Hobbs" wrote in message
>> Rene Tschaggelar wrote:
>> > What kind of frequency range and what kind of signal range
>> > are you looking at ?
>> > There are 90+something dB logamps that go to 500MHz,
>> > and the latest part I've seen does 160dB range up too 15MHz.
>> 160 dB in 15 MHz? I don't think so. Just the thermal noise in 15 MHz
>> -174 dBm+10*log(15e6)= -102 dBm. Getting a 160 dB dynamic range would
>> require a maximum signal level of 600W, assuming a 300K noise
>> What parts are these, exactly?
>> Phil Hobbs
>That sounds like the AD8304. That is a monolithic transdiode type
>logarithmic amplifier. They are intended for conditioning photodiode
>outputs. they do have 8 orders of magnitude of input current (100pA to
>10mA) and at the high end the bandwidth is in the MHz region but the
>bandwidth drops off proportionally to the input current - at 100pA it is
>pretty low - in the Khz region. Obviously there is a lot of noise. You
>need to filter the response to hundreds of Hz to get good reasonable
>response at low current.
So you can have 160 dB range and 15 MHz, but NOT both at once. That's
how 'specmanship' comes about. (;-)
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
PLEASE do NOT copy news posts to me by E-MAIL!
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup