Can You Please Show us how the two
transistors are used along with the
opamp in some kind of GIF Image
schematic ??

----- Original Message ----- 
From: 
To: 
Sent: Saturday, December 01, 2007 8:30 AM
Subject: Re: HS-10-1 questions


> 
> In a message dated 01/12/2007, psn@............ writes:
> 
> I am  using now a Burr Brown PGA204 instrumentation amp  for my tests.  Later
> I want to try a
> LT1028/1128. Does anyone know a better amp for a  400 Ohms coil?
> 
> 
> 
> Hi Andreas,
> 
>    The PGA 204 is relatively noisy
> 
>    The LT1028 is a bit better than the LT1007CN8, but  more expensive. You 
> need to design the -ve input circuit with maybe 200 Ohms max  to ground and the 
> geophone onto the +ve input.
> 
>    You can get lower noise if you use a differential  input pair of low 
> noise transistors onto a LM301 opamp or similar.
> 
>    Regards,
> 
>    Chris Chapman 
> 
> 
> 
>   
>
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