I interpreted the notes to mean that the three lower resistors in front =
of A1 were 100K, the input cap was 0.25uF, the feedback resistor was =
464K, and the feedback cap was 0.01uF.

In my implementation, I used an ordinary single op-amp for A2, as drawn. =
 It works fine, as long as you choose one (like the LM837 I used) with a =
wide input voltage range. =20

If you decide to go the instrumentation amp route, I suggest you buy a =
packaged one, like the AD620, rather than build one.  To get good CMRR, =
you need to have matched resistors all around the three op-amps. =20
Here's a link to an application note from National Semi:  =
http://www.national.com/ms/LB/LB-1.pdf

Keith
  ----- Original Message -----=20
  From: Mike Speed=20
  To: psn-l@.................
  Sent: Wednesday, December 24, 2003 9:17 AM
  Subject: Re: STM-8 Questions






      >"Integrator, Unity Gain Instrumentation Amp 20 to 200 Seconds?" =
refers >to A2 and it's related parts in the lower middle.


      On the "Block Diagram of Hardware Store Broadband Seismometer...", =
what are the component values of the all the resistors and capacitors on =
A1?

      A2 says it is a "3 amp High CMRR X1 Gain."  What is the exact =
configuration of A2?

      Greg


-------------------------------------------------------------------------=
-----
  Do you Yahoo!?







I interpreted the notes to mean that =
the three=20
lower resistors in front of A1 were 100K, the input cap was 0.25uF, the =
feedback=20
resistor was 464K, and the feedback cap was 0.01uF.
 
In my implementation, I used an =
ordinary single=20
op-amp for A2, as drawn.  It works fine, as long as you choose one =
(like=20
the LM837 I used) with a wide input voltage range.  
 
If you decide to go the instrumentation =
amp route,=20
I suggest you buy a packaged one, like the AD620, rather than build =
one. =20
To get good CMRR, you need to have matched resistors all around the =
three=20
op-amps.  
Here's a link to an application note =
from National=20
Semi:  http://www.national.com/m=
s/LB/LB-1.pdf
 
Keith

  
----- Original Message ----- 
  From:=20
  Mike =
Speed=20
  
  
To: psn-l@.............. 
  
Sent: Wednesday, December 24, =
2003 9:17=20
  AM
  
Subject: Re: STM-8 =
Questions
  


  


  

    

      
 
      
 
      
>"Integrator, Unity Gain Instrumentation Amp 20 to 200 =
Seconds?"=20
      refers >to A2 and it's related parts in the lower middle.
      
 
      
 
      
On the "Block Diagram of Hardware Store Broadband =
Seismometer...",=20
      what are the component values of the all the resistors and =
capacitors on=20
      A1?
      
 
      
A2 says it is a "3 amp High CMRR X1 Gain."  What is the =
exact=20
      configuration of A2?
      
 
      
Greg
  

  

  Do you Yahoo!?
Yahoo! Photos - Get=20
  your photo on the big screen in Times =
Square