Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Voltage to current converter in the microAmpere range

Status
Not open for further replies.

e-l-e-c-t-r-o

New Member
I just wanted to know if there is a voltage to current converter that works on a 10-200uA range instead of the normal 4-20mA one.

Or maybe I can make a XTR 110 to do that?

I'd sure like to know how.

Thanks.
 
you can design a voltage to current converter for any range of current
but your range is low so you will need an amplifier circuit and you will have to make sure placing the resistor in the ciruit doesnot effect your ciruit
for better accuracy you will have to use precision components
 
instruite said:
you can design a voltage to current converter for any range of current
but your range is low so you will need an amplifier circuit and you will have to make sure placing the resistor in the ciruit doesnot effect your ciruit
for better accuracy you will have to use precision components

So I am assuming that XTR "modification" is not possible?

Maybe another chip?

I am sure that it is possible to do a V-I from scratch, but can u propose a circuit?
The range is indeed low and I am kinda lost here.

Help, please!
 
e-l-e-c-t-r-o wrote:
Or maybe I can make a XTR 110 to do that?

XTR is voltage to current converter and I think your requirement is opposite?
So I am not able to understand how do u plan to modify XTR to achieve your target?

If you need help first let us know about your schematics.
your current is from a current source or is it from some other circuit (then you have to design your current to voltage converter in sucah a way that it does not load your previous circuit)

check this application notes for references
https://www.electro-tech-online.com/custompdfs/2005/08/sloa039a.pdf
https://www.electro-tech-online.com/custompdfs/2005/08/sboa046.pdf
 
e-l-e-c-t-r-o said:
I just wanted to know if there is a voltage to current converter that works on a 10-200uA range instead of the normal 4-20mA one.

Or maybe I can make a XTR 110 to do that?

I'd sure like to know how.

Thanks.
Do you need to use the current in a loop (like the 4-20ma ones), or is it to be used locally? What are you using it for?
Do you prefer the XTR110, or would you rather use other parts?
What is your input voltage range?
The converter shouldn't be difficult to design, and you can probably use the XTR110 if you want. Fill us in on your needs.
 
The XTR looks to be (to me) quite a hassle to make work for the microAmpere range.

So, I kinda need a voltage to current schematic that is not intended to be used in a current loop, the voltage range is 0-5 Volts, the current range is 0-200uA, made of discrete components.

Anyone?

Help appreciated.Many thanks!
 
e-l-e-c-t-r-o said:
The XTR looks to be (to me) quite a hassle to make work for the microAmpere range.

So, I kinda need a voltage to current schematic that is not intended to be used in a current loop, the voltage range is 0-5 Volts, the current range is 0-200uA, made of discrete components.

Anyone?

A simple 25K resistor is all you need!.
 
Nigel Goodwin said:
e-l-e-c-t-r-o said:
The XTR looks to be (to me) quite a hassle to make work for the microAmpere range.

So, I kinda need a voltage to current schematic that is not intended to be used in a current loop, the voltage range is 0-5 Volts, the current range is 0-200uA, made of discrete components.

Anyone?

A simple 25K resistor is all you need!.

I wish! :roll:

This converter my tutor is asking may not be used in a current loop, but he wants to be a schematic "as complicated as those used in a current loop", not just a resistor!
The main differences from common VCCs is that is not intented to be used in a current loop and it is for the microAmpere range.

He told us to find schematics on the internet for both and then analyse their differences in operation and role, I managed to find only conventional VCCs, and I am having a hard time to find the latter one.
(That's why I am asking here).

You are my last hope (sigh).

So, anybody with a schematic suggestion?
It could not be that hard to compile one from discrete components (right?),
I just need one ready-made for a reference.
I can't make one by myself cause I need the quote;plus there is always the possibility I could make it wrong.

Thanks for helping me out.
 
Back with some things to better explain.

I told my tutor about the resistor solution you suggested (thanks!), and replied:

"Our experiment refers to ways of a linear charging capacitor.
Having a resistor will charge a capacitor (existing after VCC) logarithmic over time.

The main theory behind such a VCC is the ability to feed it with a constant dc voltage (or a pulse) and output a (linear) analog signal.

You should be able to find a discrete component schematic of VCCs into applications like peak indicators and digital to analog converters."

Now can anyone help please?
At least suggest a relative link for peak indicators and Digital to Analog Converters. :oops:

:D
 
This will do what you want. If you needed it to be precise, you would need to use precision resistors, replace the BJTs with small geometry MOSFETs, and use precision op amps. As shown, you will need op amps whose input common mode range includes GND, and whose output range is nearly rail-to-rail. If you need a suggestion on specific parts, it may be some time next week, because I'm on vacation right now, and only have sporadic access to a computer.
 

Attachments

  • v-i_converter.gif
    v-i_converter.gif
    3.8 KB · Views: 1,019
Ron H said:
This will do what you want. If you needed it to be precise, you would need to use precision resistors, replace the BJTs with small geometry MOSFETs, and use precision op amps. As shown, you will need op amps whose input common mode range includes GND, and whose output range is nearly rail-to-rail. If you need a suggestion on specific parts, it may be some time next week, because I'm on vacation right now, and only have sporadic access to a computer.

Take care that U2's input bias current is not in uA over operating conditions. Use FET input opamp for higher accuracy.
 
Optikon said:
Ron H said:
This will do what you want. If you needed it to be precise, you would need to use precision resistors, replace the BJTs with small geometry MOSFETs, and use precision op amps. As shown, you will need op amps whose input common mode range includes GND, and whose output range is nearly rail-to-rail. If you need a suggestion on specific parts, it may be some time next week, because I'm on vacation right now, and only have sporadic access to a computer.

Take care that U2's input bias current is not in uA over operating conditions. Use FET input opamp for higher accuracy.
Good point. Fortunately, most if not all rail-to-rail IO op amps are are CMOS.
 
HI
I realized today that after seeing the Ron H posts that e-l-e-c-t-r-o was asking for Voltage to current converter
Previously i guess i missread and replied for current to voltage converter :(
I guess I was too habituated to design circuits for converting 4-20 mA to voltage that by seeing 4-20 mA in first post I assumed the same :(

and too my surprise :eek: nobody pointed out my mistake before :(
anyways next time I will take care to read properly before replying :)
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top