How to design a current reference?

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IC_Lee

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The precision is less than 5% at any condition , including the variation
of process , power suply , temperature and ±20％ resistance.

Thanks a lot!
 

Do you mean current source which can be used as calibration/reference?
What is the current range : 4-20mA, 0-10A....??? and max voltage???
 

Can you use external component like resistor? If so, you can use band-gap voltage (3~5% variation for all case) and a external resistor (1% variation).
 

For implementation, you can use an opamp+current mirror to realize.
 

I think to use a high PSRR opamp&a cascode mirror.
 

10%-power supply,temp from -40-->120,Vth vary about 20%,proccess ......my advice is bandgap+current buffer
 

ues bandgap cricuit and convert voltage to current
 

IanP said:
Do you mean current source which can be used as calibration/reference?
What is the current range : 4-20mA, 0-10A....??? and max voltage???
Click to expand...

Yes, the current source is use as reference.the current range is less than 1mA.
the power supply voltage is 2.5/3.3/5.
 

rtpq said:
Can you use external component like resistor? If so, you can use band-gap voltage (3~5% variation for all case) and a external resistor (1% variation).
Click to expand...

I can't use external resistor ,so I should consider the ±20% variation of resistor and its temperature coefficient .
 

Question said:
ues bandgap cricuit and convert voltage to current
Click to expand...

At present , I'm trying this way. But I meet some problem . Could you give me some detailed schematic?
 

Thanks again for everyone .
 

Question said:
ues bandgap cricuit and convert voltage to current
Click to expand...

At present , I'm trying the way. But I meet some problem . Could you give me some detailed schematic.
 

For 5V you can try the attached circuit.
For 2.5, ...3V...well..the only one solution that comes up is using simple FET transistor with Vgsoff close to 0V and a resistor connected between source and gate...this cicuit should work with voltages close to 1V++
I can draw it if you are interested...
 

Question said:
ues bandgap cricuit and convert voltage to current
Click to expand...

At present , I'm trying the way. But I meet some problem . Could you give me some detailed schematic.
 


You're so kind .Thank you very much.
I had an urge to know it.
 


The pnp transistor in this circuit can't be implemented in CMOS process .

The current will change according to ±20％ variation of the resistance Re .
 

You can replace this N-P-N transistor with a N-Channel FET..
Attached is the other drawing..
 

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