Instructables

Amplify 1.5v DC to 5+v DC?

Hi,

Anyone know if I can amplify 1.5v DC to 5+v DC (pretty much any value over 5 works) using the LM358 IC (https://www.sparkfun.com/products/9456)?

The datasheet (http://www.sparkfun.com/datasheets/Components/General/LM358.pdf) specifies the power supply range as 3V to 32V however the input voltage range is -0.3V to 32V (top of datasheet page 2). I've done some googling but I'm still not sure about the difference between these two. 

Any tips or links on wiring this guy up would be awesome,


Thanks!

Orngrimm1 year ago
If you really want to DC-DC-Convert the DC-POWERSUPPLY that can be done.
Maybe you want to power your microprozessor-Board from a single 1.5V-Battery like a D-Cell?
What you need is a Boost-converter.

There are many very simple designs freely available from linear technologies. Go to linear.com and go for "Powermanagement" --> "Switching regulator" --> "Step-Up regulator".
Now enter your values and you get an URL like http://parametric.linear.com/internal_power_switch_boost#!1646_Boost!1032_%3C=1.2!1033_%3E=1.7!1034_%3E=5!1035_3.13:9.38!vinmin_1.2!vinmax_1.7!vout_5!iout_0.5 where you find some nice chips including reference-designs for DC-DC-Conversions from a starting point of 0.5V to an output of 5V and higher with a current of 0.5A (Which i estimated should be enough for a Microprozessor-Board).

But the Item scraptopower (This 1.5V to USB from eBay) also should work... It is in fact a similar design as the ones you find at linear.com but it is ready for use out-of-the-box. So if you arent in for designing schematics and routing boards, you should go this way :)

So... I think we covered all the possibilities here:
A: You want to levelshift a 1.5V signal, than you go with the information provided in my first post and make a non-inverting amplifier with your LM358.
B: You want to boost the supply from 1.5V (Like a battery) to 5V (like for USB-powered boards) then you use a DC-DC-Converter which boosts your 1.5V-Supply to 5V. Use the linear-Chips or the eBay-Item.


"You problem is starting at 1.5 volts it is so low it's tough to do much with it."
--> 1.5V is more than enough if you use the right boost-Regulators... I made energy-harvester working from as low as 0.18V...
"DC can't be amplified."
--> Oh... Then all those Operational Amplifiers out there like the LM358 ot LTC2050 are simply lying? Good to know...

"If you google buck converter you'll find an answer."
--> Boost... Not Buck. Boost goes UP (what he needs if he want to go from 1.5V to 5V) and buck goes DOWN (5V to 1.5V) which is contrary to what he needs...
Orngrimm1 year ago
either you want to DC/DC-Boost a supply and then the LM358 is not the right chip (it is an operational amplifier) or you want to amplify a signal.
If the first: Forget it. Use a DC/DC-booster.
If second: You need to make a non-inverting amplifier with the LM358
See http://en.wikipedia.org/wiki/Operational_amplifier_applications#Non-inverting_amplifier
So if you want to boost a signal (0V = 0 and 1.5V = 1) to a new level (0V = 0, 5V = 1) then you can use the following resistors (Naming according to the Wiki-Article):

Given
Vout = Vin*(1+(R2/R1)) you get 5=1.5(1+(R2/R1)).
Solved for R1:
R1 = (3*R2)/7 or = 0.4286*R2
So if you fo for R1 = 10kOhm you get R2 to be 4286 Ohms. So since you stated you can go higher, i would pick a 3.9k resistor which would (with a R1 = 10k) result in a new level of 0V = 0 and 5.35V = 1
(Or more exactly the high level is 139/26 V)

DC is not a signal. also in order for an op-amp to give 5 volts it takes that from the Vcc pin to the amp. is you have 5 VDC on the IC then you don't need to use a circuit. just use the 5 volts you already have. oh yeah, 40 years electonics experience.
Never said DC is a signal. i ASKED if those 1.5V and 5V are signals or powersupply.
And of course you are right: You need at least 5V VCC at the OpAmp to get 5V out (Supposed you use Rail-to-Rail-OpAmp). But what i wanted to tell him is how he can make a levelshifter for his signals which i think are digital and represented by 0V for LOW and 1.5V for HIGH.

What i outlined was a levelshifter. Maybe i can "draw" something to explain:

He has:
[0-1.5V] --> [0-5V]
which wont work due to the non-matching voltage-levels.

I suggested to go like:
[0-1.5V]--->[shifter]--->[0-5V]
which works (One way but i think thats what he needs since he seems to want to read some sensors or something alike...).

I also outlined how he can make such a levelshifter by means of using a simple noninverting amplifier made with an OpAmp and also supplyed the maths to it and suggested values for the solution.

So sorry, but i dont know why you replyed to my post... I cannot find anything wrong with my post... Maybe i didnt understand something because English isnt my language? If so, please enlighten me. :)
lkndave1 year ago
DC can't be amplified. If you google buck converter you'll find an answer. I need 175 volts for a tube preamp guitar pedal and going to use a simple flyback (inductor) and a simple 555 timer to generate pulse that go to the inductor. then rectify the stepped up and done. You problem is starting at 1.5 volts it is so low it's tough to do much with it.
What do you mean by "amplify" here ? Are you thinking that you can put 1.5V in and get 5V out, with only 1.5V on the supply pins ?

The answer then is no.
I read it that he wants a step up converter. There's plenty out there.

Here's one : http://www.ebay.co.uk/itm/DC-DC-5V-1-5A-Volt-Voltage-Regulator-Convert-Step-up-USB-Power-Module-IN-1-5V-/281005294904?pt=LH_DefaultDomain_0&hash=item416d388538

Any chance you clarify exactly what you want and what for ?
I agree, but a LM386 isn't a SMPSU..