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problem in interfacing lm335 temprature sensor with lm741

 
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a4speaker



Joined: 12 May 2008
Posts: 2
Post12 May 2008 14:50   problem in interfacing lm335 temprature sensor with lm741
hi
i'm stuck in quite a simple problem. what i have to do is just take output voltage from lm335 temperature sensor and subtract 3 volts from it using lm741 subtractor.
the problem is:
when i measure LM335 sensor output standalone(not connected to subtractor circuit) it works fine and shows voltage change with temperature. but when i connect its output with lm741 subtractor, its output remains constant with temperature.can anybody help me about whats wrong?
thanx in advance
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FvM



Joined: 22 Jan 2008
Posts: 2240
Helped: 374
Location: Bochum, Germany
Post12 May 2008 15:38   Re: problem in interfacing lm335 temprature sensor with lm74
It sounds like your substractor circuit is not working correct. Did you consider LM741 common mode range? It isn't a rail-to-rail amplifier and needs a negative supply voltage.
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Audioguru



Joined: 19 Jan 2008
Posts: 368
Helped: 22
Location: Canada
Post13 May 2008 2:29   problem in interfacing lm335 temprature sensor with lm741
Why isn't the schematic attached here??
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rikie_rizza



Joined: 05 Aug 2006
Posts: 313
Helped: 20
Location: Bikini Bottom, between a rock and a pineapple
Post13 May 2008 6:01   problem in interfacing lm335 temprature sensor with lm741
I think the input impedance of 741 has cause the sensor output to be 'freezing'. Share the schematic so we all can analyze better.
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a4speaker



Joined: 12 May 2008
Posts: 2
Post13 May 2008 6:24   Re: problem in interfacing lm335 temprature sensor with lm74
ok i'm attaching the schematic

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