need EXTREMELY low level (<0.2v) boost to 1v max DC signal

ok, well we tried an experiment altering a voltage signal by using a potentiometer and while we succeeded in having an effect similar to our hypothesis, it was in fact the exact opposite reaction we were expecting.

It is now apparent that to achieve the desired effect, we need to take the signal voltage, and boost it by an extremely small amount.

Many of the boosters i've run into trying to figure all this out, are to make like 3 volts 12 or whatever, multiplying the voltage by factors of 2-4. I need like to multiply it by a factor of like 1.05 or 1.1

the voltage signal we are trying to modify varies from .1v-1v, and fluctuates between a high and low point. The device monitoring the voltage then averages the high and low point to make an average center point.

We are trying to skew the input being received by the device so that the center point (as perceived by the device) will be slightly higher than it would be reading the original signal, while preserving the scale of the low and high points.

As stated, when we reduced the signal voltage, the center point slid down the scale.

How can I do this?? Ima NOOB!

HELLLLLLP!

I was told by a local non radio shack electronics supply place, that because of the extremely low voltage of the signal voltage, most conventional (simple) solutions would not work well.

An op amp will do what you want, but do you want gain of 1.1 which will streach the signal such that instead of .1 to 1 volt you have .11 to 1.1, a difference of .99 volts instead of the original .9 volts. Or, would an offset of .1 volts such that the output is .2 to 1.1 which preserves the .9 volt difference be better?

We are looking for the simplest method available. It sounds like the first scenario you stated will work for us just fine... I'm googling op amp.

Ok, i dont think so. it says an op amp has a negative and positive output, i need a constant output.

https://www.hobbyprojects.com/operational_amplifier/non_inverter_with_gain.html

whats this? any comments?

An op amp seems to not be ideal as i read, "The output on pin 6 switches (repeatedly) from positive to negative"

That sounds like it will not work. I cannot have an output of .8 volts one moment, and -.8v the next. It seems a "non inverting amplifier" may be what i need?

Well your post makes very little sense, and it's hard to know what you've got and what you want - try posting a circuit of what you've got so far, and tell us EXACTLY what you're trying to do (and not how you're trying to do it).

But as suggested, based on the meagre information so far, an opamp should do what you want?.

This is the kind of thing you need:

evotec1 said:

I was told by a local non radio shack electronics supply place, that because of the extremely low voltage of the signal voltage, most conventional (simple) solutions would not work well.

Click to expand...

Don't liston to what they tell you at Radio Sh@g, they don't know what they're talking about!

They're only shop workers, they don't know anything about electronics!

Hero999 said:

Don't liston to what they tell you at Radio Sh@g, they don't know what they're talking about!

They're only shop workers, they don't know anything about electronics!

Click to expand...

I know I asked one if he had any background or training in electronics.... He said he was a former schoolteacher, lol

Nigel Goodwin said:

Well your post makes very little sense, and it's hard to know what you've got and what you want - try posting a circuit of what you've got so far, and tell us EXACTLY what you're trying to do (and not how you're trying to do it).

But as suggested, based on the meagre information so far, an opamp should do what you want?.

Click to expand...

Whats your deal? I saw you posting this EXACT post to someone else's thread. Do you have it like on a preset or somthing? I'm a noob at this, i was even having a difficult time getting this forum to work, so please go easy on me.

I think i made it perfectly clear what i need, as others have been able to lend kind assistance from whatever non technical information I have provided.

And finally, RusselK!

You are the man. Thank you so much for helping me through this, your answers have helped me more than i can tell you. I have found similar diagrams, but i really dont understand a lot of things i am reading about this circuit.

Will it be able to provide the circuit with a constant voltage boost?

can anyone provide me with some basic knowledge about what is happening in the diagram russelk here has provided? I will be much more comfortable working on this if i feel i have a grasp of the big idea

like this.... i wasnt much into algebree in the high school..

R2
Vout= Vin ( 1+ --- )
R1

but then it says Zin=infinity

I dont see a z in anywhere

then it talks about a third resistor of value Rf||Rin added between the Vin source and the non inverting input

If you are confused, i am looking at the wikipedia entry for "operational amplifier applications.... here, https://en.wikipedia.org/wiki/Operational_amplifier_applications

I'm confused by ALL of this, so any help, would be AWESOME!!

A typical exchange after walking into Radio Shack:


"Can I help you?"

"No, I know more about what I'm looking for than you do..."

I remember (when I was a child) asking a shop assistant at Maplin how many transistors one of the melody generators they sold contained, they said "about 20". I don't think so they were just giving me the usual bs!

The input impedance of the op amp is high already (megohms) and is multiplied by some factor of the gain which makes it so high it would be difficult to measure. There is bias current at the input, about 100 nA which is small enough to neglect in this circuit. Where the Wikipedia article says Rf||Rin, it should have said R1||R2. But, again, the bias current is neglectable. There will be several millivolts offset at the output which can be trimmed out but might require a negative voltage.

so the output will not be the input plus the boosted amount? what is offset?

Hero999 said:

Don't listEn to what they tell you at Radio Sh@g, they don't know what they're talking about!

They're only shop workers, they don't know anything about electronics!

Click to expand...

---Insert remark about who you are/where you live/race/gender/employment here---, but then that would be a stereotype. Maybe you should think before grouping all RS employees into your stereotypical belief about them. RS does not train its employees on circuit theory. The components are in the parts drawers and you should know what you need. There are even pictures on the front of the drawers if you can't read. I will agree with you that most RS employees do not know the first thing about building a circuit, but you have to keep in mind that they are not trained to be your electrical engineer for your project, they are salesmen/women. If they cant point you in the right direction for what you asked then they are either new, or maybe stupid; but don't go saying no-one at RS knows anything about electronics because that just isn't true. I work at RS and know a hell of a lot about electronics and microcontrollers. I couldn't see making a career of it, but to help pay bills during college to get an electrical engineering degree it is not a bad place to work. ( discount on what little parts RS still sells ) Sorry to hijack your thread evotec, but I couldn't let this one go. This isn't a personal attack Hero, I'm just sick of the lumping of all RS employees into one pile of idiots. -Jacob

ok, this isnt a buzzing RS post, its a help i'm a noob post... any explanations of what russlk said?

evotec, from your original question, this is how i interpreted it. Your signal has a range of 0.1 to 1.0 volts. Your device reads this voltage over some time period and then gives your the median value of all values recorded(center point). While setting the gain of the op-amp at 1.05 or 1.1 as mentioned would probably work, you might try setting the op-amp up as a 'non-inverting summer'. Take your actual signal voltage and the amount you wish to shift your signal, and add them together. Say your shift voltage was set at 0.2 volts, the range of the output signal would then be 0.3 to 1.2 volts. This would only shift your signal voltage instead of multiplying it. Check out this link for more info and diagrams. Make sure to set the gain at 2 instead of 3. Their examples show summing 3 voltages. -Jacob

Awesome! I'm checking it out.