negative voltage reference

[avinash]

i need a -1.25V voltage reference which also tracks the VSS.in my case vss is -2.5.actually i need to convert this voltage reference to current reference using v-i converter.now one terminal of resistor is vref(-1.25) and other terminal is vss(-2.5). thats why i need a vref that also tracks the vss so that voltage across the resistor do not change so that i get constant current.
now my question is that is there any vref available in market ,or there is any another way out to generate constant current.

 

[Davood Amerion]

voltage reference is 2 pin device (in 3 pin TO-92 package),
and can be used to produce positive or negative voltage reference.
If you connect positive pin to GND and negetive to -VCC through
resistor you will optain negative reference.

 

[avinash]

if i connect gnd at one pin and vcc at other pin ,from where or which pin will provide me voltage reference.

 

[IanP]

Check out this link:
https://focus.ti.com/lit/ds/symlink/ref1112.pdf
It describes 1.25V shunt reference .. all what you need to do is to connect a resistor (see text for its value calculation) between -2.5V and the anode, whereas the cathode will be connected to GND ..
So, you will have (-2.5V)-->resistor-->(-1.25V)-->diode-->0V ..
Regards,
IanP