[sdiy] converting a 10v p to p to a 0-5 volt signal

[Scott Gravenhorst]

Dan Snazelle <subjectivity at hotmail.com> wrote:
>
>yes i have the opamp cookbook.  where should i look?
>
>also the problem i seem to be having is this. i can get the 
>signal in the right range for one input. but then when i add 
>another input its in the wrong range. 
>
>i feel very very dumb right now
>
>thanks so much

Look for that parts the show how to control gain 
and how to "inject" an offset [or really, how to use/configure the summing node].

For example, for an input expected to go from -5.0 to 5.0 volts and have a corresponding output
of 0.0 to 10.0 volts, you want an offset of 5.0 volts and a gain of unity (one).  So you would
use an opamp to give you a gain of 1.0 but add 5.0 volts to whatever the input is.

Gain and offset together can be used this way to make the conversions you're interested in.  

The offset voltage is input into the summing node (as is the input signal) and the gain is
controlled by the feedback resistor.  Gain and offset then create on operational formula:

Output = Gain * ( Input + Offset )

Each scenario you probably want is a combination of different values in that formula.  What
might make sense for you in your modular is to have an amplifier where you can control the gain
(use a pot for the feedback resistor) and an offset voltage that is added to your input signal
(again, a pot, but set up as a voltage divider from +v to -v feeding the summing node through a
resistor).


>>>
>>>tonight i was looking at my scope
>>>
>>>Checking the input into a circuit that was only able to take 0-5 volts
>>>
>>>Sure enough, the signal was between 0 and 5 but the sawtooth was clipped.
>>>
>>>So i am looking for a input block that can take either
>>>5vp to p or 10v p to p (or any synth signal)
>>>and spit it out as a 0-5 signal without squaring the top.
>>>
>>>
>>>anyone know of a good circuit for this?
>>
>> Dan,
>>
>> Now is the time to become seriously interested in Operational Amplifier theory. A
>> linear DC amplifier is what you want. A good book will make many things like this
>> possible.
>>
>> -- ScottG
>> ________________________________________________________________________
>> -- Scott Gravenhorst
>> -- FPGA MIDI Synthesizer Information: home1.gte.net/res0658s/FPGA_synth/
>> -- FatMan: home1.gte.net/res0658s/fatman/
>> -- NonFatMan: home1.gte.net/res0658s/electronics/
>> -- When the going gets tough, the tough use the command line.
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>

-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
-- FPGA MIDI Synthesizer Information: home1.gte.net/res0658s/FPGA_synth/
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- When the going gets tough, the tough use the command line.