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### Topic: non-inverting OpAmp (Read 824 times)previous topic - next topic

#### navab1362

##### Oct 12, 2017, 08:06 am
Hello,
I want a simple circuit for amplifying low voltage by using single supply Op Amp.
Input voltage is about 2.2 V. I want output be 5V.

#### Southpark

#1
##### Oct 12, 2017, 08:37 amLast Edit: Oct 12, 2017, 08:41 am by Southpark
Maybe this...

The 470 ohm resistor is "R1". The 600 ohm resistor (set by the potentiometer) is "R2". The linear gain (aka voltage amplification factor) for this configuration is  1 + (R2 / R1)

#### Wawa

#2
##### Oct 12, 2017, 09:38 am
I want a simple circuit for amplifying low voltage by using single supply Op Amp.
Input voltage is about 2.2 V. I want output be 5V.
If you change default Aref to 1.1volt Aref, then an A/D value of 1023 is already reached at ~1.1volt.
Drop your 2.2volt to ~1volt with a voltage divider, and switch to 1.1volt Aref in setup().
Then you don't need an opamp.

https://www.arduino.cc/en/Reference/AnalogReference
Leo..

#### TomGeorge

#3
##### Oct 12, 2017, 11:57 am
Hi,
What is the application.

Does your input just go from 0V straight to 2.2V, as in a pulse, and back again.
OR
Does your voltage move between 0 and 2.2 over a period of time and you want an output of 0 to 5V over that same time.

These are two different types of signal and they can be changed to 0 to 5V output in two different ways.

Thanks.. Tom...
Everything runs on smoke, let the smoke out, it stops running....

#### MarkT

#4
##### Oct 12, 2017, 12:17 pm
Hello,
I want a simple circuit for amplifying low voltage by using single supply Op Amp.
Input voltage is about 2.2 V. I want output be 5V.
Most opamps don't swing outputs all the way upto the +ve rail.  A signal at 2.2V is already
in a good place to A->D convert.

Perhaps you should say more about what the signal is and why you think it needs amplifying,
because I'm not convinced it does.

You haven't said what bandwidth or accuracy are wanted either, which might be important.

The example circuit above could have its resistor values changed to 4k7 and 10k pot, most
opamps are happier (work better) with lighter loads.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### navab1362

#5
##### Oct 20, 2017, 07:30 pm
Thanks for assisting

#### DrAzzy

#6
##### Oct 20, 2017, 07:49 pm
Most opamps don't swing outputs all the way upto the +ve rail.
Some don't, but opamps with rail to rail output are readily available nowadays, and are no longer an exotic part.
ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

#### Southpark

#7
##### Oct 21, 2017, 01:59 am
Some don't, but opamps with rail to rail output are readily available nowadays, and are no longer an exotic part.
Hi DrAzzy, do you have a nice list of rail-to-rail op-amps that you normally use? Ones that supercede all the general non-rail-to-rail ones?

#### MarkT

#8
##### Oct 21, 2017, 04:07 am
Parametric search at an electronics supplier's website is a good place to start.  There are many many
thousand of parts out there with new ones all the time.  With opamps there are about a dozen
different specs to worry about, what's important for one application may be unimportant for another,
for instance:

supply voltage range,
PSRR
CMRR
low noise
bandwidth
offset voltage
input current
output current
slew-rate
power consumption

and more...

One that is a very good all round performer that I've used is the AD8656, but its limited
to a maximum 5V supply. and its not cheap, but its very low noise, high bandwidth, high
output current and good rail-to-rail performance.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### ChrisTenone

#9
##### Oct 21, 2017, 05:22 am
Thanks for assisting
Hey Navab, care to give up more than that? Believe it or not, there are people here who would benefit from your exploration.
Atmosphere carries combustion vapors to places where they will do good instead of harm - Mike Faraday's 'History of a Candle': https://www.youtube.com/watch?v=6W0MHZ4jb4A

Whoops

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