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

#### 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 ?

#### MrChips

Joined Oct 2, 2009
21,281
Attenuate the signal by a factor of 2 and subtract 2.5V.

#### 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?

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.

#### crutschow

Joined Mar 14, 2008
25,103
For example, if the input side were 0V, would you get -2.5V output?
No.
The output of the circuit will be -5V when the input is 0V since the transistor is off under those conditions.

#### OBW0549

Joined Mar 2, 2015
3,437
The TS did state that he needs to shift an analog signal.

#### DickCappels

Joined Aug 21, 2008
6,451
Differential amplifier will to it in a heartbeat. Well, maybe two heartbeats.

#### 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.

#### crutschow

Joined Mar 14, 2008
25,103
The TS did state that he needs to shift an analog signal.
Egg on my face.
Obviously I missed that very important word.