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ECG circuit development

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saurabh17g

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I am planning to use INA 333 opamp for amplifying the low voltages(in microvolts) given out by sensors. But as my device is battery operated, i am unable to provide +(7 pin) and -(4 pin) voltages. I want to operate my circuit in a single supply mode instead of dual supply. As specified in website INA 333 is single supply opamp but it dint work. Will anybody help me in debugging this problem.

Also, if anybody has any document about internals of opamp(which is a differential opamp) to get to know about the equations and other details, please give me the links.
 

saurabh17g

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Could you post the circuit of what you tried but didn't work?

Keith
I do not have a circuit simulator, however, my connections are simple:

connections- 5-ground,4-ground,7->+2.5V(+V),2-ground,3->0.0001V(input DC voltage to be amplified). resistance(RG between pins 1,8 ) = 12k ohm. It works when 4 pin is connected to -2.5V. But in actual circuit(ECG), i would not be able to provide it since it would be inside person's body. I want to manage it with minimum power and voltage requirement.
I have attached the datasheet of this part. Please refer to fig 32. Just did bare minimum connections to make the part work.
 

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keith1200rs

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If you want single supply operation you simply connect V+ to your positive supply and V- to GND. Then you need to make sure the REF is connected to sensible voltage such as half V+, NOT to GND.

Keith.
 

bobcat1

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Hi

Search Analog device site for ECG - you will find some application note & ref design schematic for 3 ch ECG

All the best

Bobi
 

Sink0

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Man .. just use the circuit at page 15. I would use a different DRL but the circuit itself is a very good example.
 

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