should be a simple op amp question

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cyberblak

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Hi all,

I need to design a signal amplificator with the following specs :

input signal : 0mV - 100mV
output signal : 0mV - 3V (not inverted)

The input signal comes from a shunt resistor that monitors a current.

I know how to do this, but I have the following constraints :

- use only 1 opamp
- no negative supply (the amp should be single supply)
- 0 should be a true zero (most rail to rail opamps still can't go to 0)

Any ideas?

I thought of adding a small bias to the input signal so that the output wouldn't need to go to zero (this is the main issue right now). I can remove this offset by software later. Is it a good idea and how to do this?

Thanks all

cyberblak
 

you can use TLC272 which it's output voltage include zero [ in non-inverting configuration mode ].
Or use Rail to rail op-amp.
 

If your supply is to be connected to one side of shunt - there will be problem you mentioned (you can try to use capasitor based DC DC converter , even simple RS232 driver can suffice for you - some of those have converted voltage outputs , or other specifically designed for this purpose converters) , but if not - make a virtual ground for opamp via 2 resistors and capasitor and connect it to one side of shunt .
 

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