PSN-L Email List Message

Subject: RE: amplifier noise
From: "Dale Hardy" dale@...........
Date: Sun, 7 Jul 2013 09:47:31 +1000

Hi Bob, the 741 is a good GP amplifier, once you refine your circuit you can
use better low noise op-amps.
To test, Try running you circuit from batteries, the switch mode supplies
may be generating heaps of noise/hash


-----Original Message-----
From: psnlist-request@.............. [mailto:psnlist-request@...............
On Behalf Of Bob Smither
Sent: Sunday, 7 July 2013 7:43 AM
To: psnlist@..............
Subject: Re: amplifier noise

On 07/06/2013 01:04 PM, JAMES RIDOUT wrote:
> Hello all, Sorry to be a pain, But ive just built the two 741 opamp 
> circuits, Ive been very carefull with construction, but in getting a 
> lot of noise!, if I unplug the feed from the coil im getting the data 
> value (in amaseis), jumping about 1000 points +&-.
> im using two 12v switch mode power supplies.
>   Im not great at electronics, but I know the basics.
> Im using a dataq 194.
>   Any help would be great!.
>      Thanks,   James

Hi James,

The 741 is not considered a low noise amplifier.  Take a look at the Linear
Tech LT1007, for example.

It would help determine if what you are seeing is expected if we knew:

  circuit diagram (do you have link?)
  brand / model of power supply (switch mode is often pretty noisy)

The Dataq 194 is only 10 bits (counts of -512 to +512) so not sure I
understand the +/- 1000 counts observed.  Maybe something from Amaseis (I
don't use that)?

Bob Smither                                 bob@...........
"Personality is the supreme realization of the innate  idiosyncrasy of a
living being.  It is an act of high  courage flung in the face of life, the
absolute  affirmation of all that constitutes the individual, the  most
successful adaptation to the universal conditions of  existence coupled with
the greatest possible freedom for  self-determination."
  --C.G. Jung


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