DC offset adder

[Jony130]

Hi, do yo know any simply circuit that can add a DC-offset voltage to the output signal form temperature sensor?
For example we want to add 0.5V to the signal that change linearly from 0.1V to 1V.

 

[NorthGuy]

A voltage divider between the output and VCC?

Depending on your needs, you may follow it with an op-amp buffer.

You get V = (Vsensor*Rvcc + Vvcc*Rsensor)/(Rvcc + Rsensor). This will add an offset, but also will attenuate your signal a little. If you don't want attenuation, you can amplify the resulting signal with an op-amp, which is very easy if you already have an op-amp working as a buffer.

 

[Jony130]

Thx, that's very good idea.
https://www.google.pl/url?sa=t&rct=...=cABoS2Ay0WxPcBLIRBC-vA&bvm=bv.61725948,d.bGE

 

[MrAl]

Hi,

I like Northguy's idea too.

Another method if your sensor does not have to be grounded is to connect a voltage divider center tap to the negative terminal of the sensor and bias it with Vcc. This gives a lot of flexibility of the two resistor values. The output of the sensor positive terminal is then the sum of the differential sensor output and the bias voltage, after load impedance is considered also.

For example, if you want 0.5v offset and you have a stable +5v supply available the ratio is 10 to 1, so the upper resistor is 9 units and the lower is 1 unit. Some resistor value pairs that work then are:
9 Ohms and 1 Ohm,
90 Ohms and 10 Ohms,
900 Ohms and 100 Ohms,
9K and 1K,
90K and 10k,
etc.

The best choice depends on the load impedance and the amount of current that can be spared to drive the voltage divider bias network and of course the desired accuracy.