# Need a current source about 100uA...1mA

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#### H_u_n_t_e_r

##### Full Member level 2
National LM334 hasn't good tempco..
Im planning use it on 1000Ohm RTD sensor.
Regards.

#### Hishamsaleh

##### Full Member level 1
Use sweap generators or Boot-Strab current source... the error is about 2~5% max... it's really powerfull...

#### ttosolee

##### Member level 1
i think you can use the following app.note.

#### Hishamsaleh

##### Full Member level 1
circuit

have a look.. this is the design of bootstrab generator... you can have the current sourse from the diod and Q2 withoutr all other components... so that you do not have delta pulses of current... it's working.. i'm using this method.

#### H_u_n_t_e_r

##### Full Member level 2
Thanx to all reply..But %5 error too big.
There is another Current reference is REF200(from BurrBrown-Texas)
its excellent %0.5 error but difficult to find for me and expensive 5$each...2.5$ for 1K...

Regards.

#### Cluricaun

REF200

Hi H_u_n_t_e_r

I havent used this chip myself but if you like to try it and do not need so many, then try to get it as a sample. TI is really generous and you can have the chip within 3-4 days.

Good Luck

#### KamW

If you would like to get precision temperature measurements, maybe it would be better to use "poor" tempco current source, and connect RTD in series with stable resistor. Then measure resistor voltage drop, calculate current -> RTD -> temperature
;-)

regards
KamW

#### tjalps

##### Full Member level 5
Hello!

I have intention to build similar aplication with NTC resistor. What do you think about use of voltage reference 2.5V?

Regards!

yma-313

Points: 2