Electric Circuit Requirements

Provide some solid information for readers to work with, and the help may come.

thanks for the response.

Can you please ask me the information what you need ?

so that I can help you with that, do not mind am a starter and I am really trying to learn.

regards,

Mirza.

<...I am trying to build...>

Is someone else going to design it, then?

Radio antennae produce picoamps.

I think if i check out the circuit of radio antenna it is enough for me.

OK _{<unsubscribes>}

if you can help me more with this, it will b more helpful thanks.

It is nice to know that you are a learner. But a learner must first decide what you want to learn. You say you have a power supply. What power supply AC or DC? What voltage? Then you want to convert it to what supply to drive a current? What type of Electronics? These are the basic information you must know. Then you must have a clear picture in your mind as to what is the project you intend to make. If all these information is provided here some experienced engineer or scientist here can help you.

a source for such small currents can ~be made in many ways! and you don't even need to make a very sophisticated circuit. a resistor can easily limit the output current! what is the application for?

You might be able to utilize a signal generator...

https://www.allelectronics.com/make-a-store/item/MK-105/SIGNAL-GENERATOR-KIT/1.html

https://www.linear.com/product/LT1008

This might work...

http://www.cs.rdm-apps.com/

Use the available voltage and Ohm's Law to calculate how much resistance you need.

as the voltage is 12 volts,

and currents must be around -10 pAmps to 10 pAmps the resistor value is going up to 10e12 (tera). is there any other way to decrease the resistance value to mega ?

may be voltage regulator or something can work ?

Maybe you can describe what you will be connecting this picoAmp source to...

this circuit will be connected to other potentiostat circuit to test the results of the potentiostat.

What circuit?

What test?

What results?

Do you have a drawing of what it is?

Following through on reading this might give you some insight A generator for very small direct currents

Thank you so much for your detailed answer.

That's a pretty darn good answer (PDGA), marcot.

The amount of current will be determined by the load. All power supplies can produce as little as zero amps if required.....

Are you wanting to limit the output current or what?

What will these picoAmps be doing?

Like nearly everyone else here has asked...What are you really trying to do?

thanks for your reply,yes here am trying to get an output current of very low value, around pico amps.

Are you ever going to answer the many questions that have been posed in this forum for you with some real information, mirzaipc, or are you going to spend the rest of your life faffing about?

I'd still like to know exactly what it is you are wanting to apply this very small, possibly precisely controlled, current to.

Any how, if you search for "precision current source" you will find gems like

http://www.ti.com/lit/an/sbva001/sbva001.pdf

or

http://www.analog.com/library/analogDialogue/archives/43-09/current_source.html

Don't know about picoAmps though..... if you used a voltage divider network in the reference voltage source you might be able to translate it down..... or not.

What is your level of empathy for things electrical?

You could clamp or weld 2 pieces of dissimilar metals together [a thermocouple ] sit them in the sun, then you could measure some pico amps between them.

Please resolve your need for+/- 10pA a couple of ways:-

Load resistance or voltage drop, and how accurate do you need the current?

I have over 50 years pA/fA background and at the world's most isolated university, diy was way ahead of six month's delivery, after the grant next December.

Leakage currents and inaccurate resistors were the main problems but I found a solution using a capacitive current splitter.

An airspaced capacitor with electrodes supported on insulators mounted on a guard/ earth plane has no significant current leakage.

The capacitor can be defined by the diameter of a hole in an earthed shield between the driving and load plates.

To generate a pA current the driving plate must be fed a steadily rising/falling voltage and easiest is the 'sawtooth out' from an oscilloscope. Feeding some microamps into a 100 nF capacitor will also provide a suitable ramp.

Of course building or buying a ramp generator could be considered, but a Keithley 610 or its A B or C version will provide the current.

Lots of people are trying to help you.

Please explain what you are trying to accomplish and please explain how you think you want to do it.

You will also have the task of developing or finding test equipment that can detect your success.

There are some genius people here, but it's almost impossible for the best people to help you because we all stall out in your first sentence "something around -10 picoAmps". We might be able to help you build something with a range limited to only 0 to 20 pico amps, but that is going to be a very challenging project unless you are working in a lab environment as the other posters have already mentioned.

And, CR4 posters, unless I've gone completely nuts since last night, please tell me that negative Amps might be imaginary or a theoretical construct but not real and measurable, right? Am I going to have take physics again?

Volts below a zero reference plane, yes. If you are describing pushing electrons into and out of a substance, there could be a varying amplitude and/or frequency and/or voltage, and many other variables.

You can have a positive number of (x) amps created by pushing electrons one direction with a negative voltage, and a positive number of (x) amps created by pulling the electrons back out with a positive voltage. And you can reverse this by changing the charge or the cathode and anode but long before we get off into that ---

Please go through all the responses to your original post and answer the questions the members have asked.

Start with - what kind of power supply do you have?

+/-ve amps is only the direction of the flow out or in of the source + terminal. The real electron flow is actually reversed from the current convention.

This is not like a negative volume that is not physically possible.

Yes you can have negative current. It normally accompanies a negative voltage. All relative of course.

Current is a vector so it has amplitude and direction.

thank you all for your responses,

the source voltage was +12v DC,using a Faraday cage got rid of external EM and noise was neglected.

I got it using a voltage divider of 240ohms and 6 ohms with load of 5 giga ohms.

Thank you again.