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 Popelish
Organization: This space not available for advertising.
X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Op-amp configuration question
Date: Wed, 02 Oct 2002 01:15:03 GMT
NNTP-Posting-Date: Tue, 01 Oct 2002 21:15:03 EDT
> I've got a schematic with an op-amp configuration I have never seen
> before. It's purpose is to take a 6.2V reference and amplify it to a
> 10V reference used elsewhere. It's set up like a non-inverting
> amplifier with the 6.2V to the + input, and a 10k R1 and a 16.5k R2
> for the divider at the - input. This much I understand. Where it
> confuses me is that there is a 332 ohm resistor pulling the output up
> to 15V, and a 383 ohm resistor from the output to the + input. What
> are these added components used for? The amp is a LT1014 and the 10V
> is used for pressure transducer excitation. Thanks for your help.
I have used this exact circuit (with slightly different values). the
383 ohm resistor provides a regulated current source to the 6.2 volt
reference. Unfortunately, if the opamp has an offset voltage in one
direction, it will lock up with zero volts out and zero volts in on
both inputs. The pull up to +15 makes sure that the output cannot
saturate close enough to zero to allow the normal range of input
offset voltage to lock the the output saturate negative. I got caught
with this problem, once, after the circuit went into production.
About 1 unit in 20 would not fire up. Had to add the pull up as
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup