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Reply-To: "Daniel A. Thomas"
From: "Daniel A. Thomas"
Subject: Re: Hot Op-Amp!
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Wed, 23 Oct 2002 00:12:24 -0400
NNTP-Posting-Date: Wed, 23 Oct 2002 00:12:45 EDT
"Amplifiers do and oscillators don't."
Oscillations? Check the mfg's data sheet and literature.
Is this part unity gain stable? Bypass on pwr supplies?
"Rileyesi" wrote in message
| I made a PCB that has four TI (Burr Brown, actually) OPA547 op amps.
| them is getting REALLY hot while the other three are not. They are
| from the same power supply (+12/-12). They are all configured for
| non-inverting operation and the three cool ones are set for a gain
of 2 while
| the hot one has a gain of 1. The test I ran was with no inputs on
all four op
| The way I am getting this is by using two feedback resistors. R1 is
| inverting input to ground and R2 is from the output to the inverting
| The gain formula is Vo=Vin*(1+R2/R1). On the hot op amp, I am using
| wire for R1 and R2 (as was suggested from this newsgroups, or maybe
| sci.electronics.basics??) Maybe I need a resistor at R1 even though
I want 0
| ohms for R2??? On the three that have a gain of two, I am using
| ohms. If I do need an R1 resistor, what value?? I'd like to use
the 3.01 k
| just for commonality of parts.
| Also, I know that running an op amp where the output is at the
midpoint of the
| power supply is the worst case for heat disipation. My inputs will
not go less
| than ground, so I intend to change to a +12/-5 V power supply which
| in the heat problem...right??
| Any thoughts would be appreciated.
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