# Bias a Signal challenge

#### Tony Elliott

Joined May 8, 2015
158
I need to bias +/- 5v to 0 - 2v signal. The challenge is +/- 5v oscillators goes into a mixer which will will go up and down in amplitude as I use my mixer. When converted the base of the signal needs to stay at ground. Is there a change I can try on my schematic. The one pictured is a tried and tested example.

#### KeithWalker

Joined Jul 10, 2017
1,919
Can you re-phrase your question so that it is a little clearer please. I can not understand exactly what you are asking.
Please explain what the "mixer" is. Is it an electronic signal mixer and what is it mixing the oscillator signal with. Is it connected to the output of the circuit?
What is the frequency of the oscillator signal?
What is the box on the diagram marked A ....K? It is not doing anything the way it is connected.
Regards,
Keith

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#### Tony Elliott

Joined May 8, 2015
158
Can you re-phrase your question so that it is a little clearer please. I can not understand exactly what you are asking.
Please explain what the "mixer" is. Is it an electronic signal mixer and what is it mixing the oscillator signal with. Is it connected to the output of the circuit?
What is the frequency of the oscillator signal?
What is the box on the diagram marked A ....K? It is not doing anything the way it is connected.
Regards,
Keith
The oscillators run from 1hz to 9999hz at +/-5v into a electronic signal mixer. Then these signals need to be biased up to 0-2v. This would be easy if the oscillators weren’t being mixed +/-5v bi polar. I need the base of the signal to stay at ground the being mixed by the bipolar mixer.

#### ci139

Joined Jul 11, 2016
1,696
... , ? -- try inverting config for the uppermost Op Amp
// my reasoning goes here that the non-balaced inverting and non-inverting inputs may develop some "temporary" offset drift
/// ... tough -- the offset drift might be present and in the "Line In" signal
//// - all offset errors must be addressed - ? how big is your error (you complain about)
+
what purpose serves the "replicated" SG (the lowermost Amp ... supposedly with some tiny offset error)
_______________________
about the complexity of the "all offset errors"

( at 1-st i rather won't explain "the below" -- would make it more complex to understand -- than just the visual inspection )

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#### KeithWalker

Joined Jul 10, 2017
1,919
Why not do it the simple way? I don't know what your supply voltage is so I can't suggest a fixed value for the offset resistor.