## PSN-L Email List Message

Subject: two-stage Roberts circuit amplifier
From: Barry Lotz barry_lotz@.............
Date: Sun, 27 Dec 2009 18:45:20 -0800 (PST)

```Chris

"=A0 Chris
=A0=A0=A0=A0 I found the abstract and filter diagram on John Lahr's web=0As=
ite. 1) I am not sure how the=A0 max gain is chosen. Is it based on the=0Ad=
ifference between the actual sensor low frequency corner and the=0Adesired =
low frequency corner given a 40 db /decade dropoff?=A0 2) I=0Aassume the tw=
o single pole circuits identical 3)=A0 Do the other values=0Ain the example=
circuit remain the same except as you have commented on?=0A4) If I want a =
lower corner frequency of 0.03 hz is the "lower turnover=0Afrequency (1/2 P=
i C1 R2)" =3D 0.015 hz? It is probably obvious I don't=0Ahave the full repo=
rt."

I realize that R3,R7 & R11 are offset resistors. How does one determine the=
value of R5 and R8 or does it matter?
Regards
Barry

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Chris" =
; Chris  &nb=
sp;  I found the abstract and filter diagram on John Lahr's web=0Asite=
.. 1) I am not sure how the  max gain is chosen. Is it based on the=0Ad=
ifference between the actual sensor low frequency corner and the=0Adesired =
low frequency corner given a 40 db /decade dropoff?  2) I=0Aassume the=
two single pole circuits identical 3)  Do the other values=0Ain the e=
xample circuit remain the same except as you have commented on?=0A4) If I w=
ant a lower corner frequency of 0.03 hz is the "lower turnover=0Afrequency =
(1/2 Pi C1 R2)" =3D 0.015 hz? It is probably obvious I don't=0Ahave the ful=
l report."I realize that =
R3,R7 & R11 are offset resistors. How does one determine the value of R=
5 and R8 or does it matter?RegardsBarry
```