Constant Current Source (CCS)?

hi all,

I want to get 1ma from the CCS like the circuit below

**broken link removed**


But due to J113 is difficult to find,

Can i use 2SK30A (JFET) instead of J113?

Should i change the resistor(1k5) in order to get 1ma?

Thx everyone ~

Hong Kong is a nice place to get electronic components especially Wah Fei in Ap Liu Street.

The 2SK30A datasheet shows that Vgs for 1mA is around -1.5V so using a 1.5K resistor is good for a start.

However, each one of 2SK30A could differs a bit and you'll need to trim the resistance to get an exact 1mA.

Also you have not shown in your circuit what sort of voltage is across the CCS. The 1N5297 is a 0.5W rated current regulating diode while the 2SK30A max Pw is only 0.1W.