Level shifting signal from +5V/-5V to GND/-5V with op amp

Thread Starter

Jorj

Joined Sep 30, 2015
19
I need to shift analog signal from +5V/-5V to GND/-5V with op amp.
It looks easy but I've tried few circuits from here and there, none of them turned out to be a success.
Can you point me in the right direction ?
 

OBW0549

Joined Mar 2, 2015
3,437
Make a 2:1 voltage divider from two equal resistors (e.g., 10 kΩ), with the top end connected to your ± 5V input signal and the bottom end connected to -5V (generated by a -5V voltage regulator or voltage reference). The junction of the two resistors is your GND/-5V output which you can buffer, if desired (to make its voltage independent on any output loading), using an op amp configured as a unity-gain buffer. (The op amp, of course, has to be powered by suitable supply voltages which are compatible with the input/output signal range.)
 

crutschow

Joined Mar 14, 2008
25,103
Here's the LTspice simulation of a one-transistor circuit to do the level shifting.
How close to 0V does the output need to go?

upload_2017-11-24_8-37-26.png
 
Last edited:

ebeowulf17

Joined Aug 12, 2014
3,274
Here's the LTspice simulation of a one-transistor circuit to do the level shifting.
How close to 0V does the output need to go?

View attachment 139998
Does this circuit scale all intermediate voltages in a linear way, or does it only work as a digital level shifter?

For example, if the input side were 0V, would you get -2.5V output?

I'm assuming you'd need a more complicated circuit to get the kind of linear response I'm asking about, but sometimes there are clever tricks I'm overlooking.
 

Thread Starter

Jorj

Joined Sep 30, 2015
19
Yes the signal is analog so I can only use voltage divider or the op amp.
I'm leaning more towards op amp solution as there won't be any loss in resolution.
 
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