I have not tried this yet, there are simple current limiting diodes available. Its should be easy implementation and they are available at Mouser.com
I want 1mA for my use so I have ordered the 1N5296 to allow more current one could connect multiple diodes in parallel.
Gill
Here is a link to PDF datasheet for current limiting diodes:
http://www.centralsemi.com/PDFs/products/1N5283-5314.pdf
1N5283 THRU 1N5314
SILICON CURRENT LIMITING DIODE DESCRIPTION:
The CENTRAL SEMICONDUCTOR 1N5283 series
types are silicon field effect current regulator diodes
designed for applications requiring a constant
current over a wide voltage range. These devices
are manufactured in the cost effective DO-35 double
plug case which provides many benefits to the
user, including space savings and improved thermal
characteristics. Special selections of IP (regulator
current) are available for critical applications.
MAXIMUM RATINGS: (TL=75°C) SYMBOL UNITS
Peak Operating Voltage POV 100 V
Power Dissipation PD 600 mW
Operating and Storage Junction Temperature TJ, Tstg -65 to +200 °C
FEATURES:
• High Reliability
• Special Selections Available
• Superior Lot To Lot Consistency
• Surface Mount Devices Available
ELECTRICAL CHARACTERISTICS: (TA=25°C)
Notes: (1) Pulsed Method: Pulse Width (ms) = 27.5 divided by IP NOM (mA)
Type
Regulator
Current
(Note 1)
IP @ VT=25V
Minimum
Dynamic
Impedance
ZT @ VT=25V
Minimum
Knee
Impedance
ZK @ VK=6.0V
Maximum
Limiting
Voltage
VL @ IL=0.8 x IP MIN
-------MINmA NOMmA MAXmA MΩ MΩ V
1N5283 0.198 0.22 0.242 25 2.75 1.0
1N5284 0.216 0.24 0.264 19 2.35 1.0
1N5285 0.243 0.27 0.297 14 1.95 1.0
1N5286 0.270 0.30 0.330 9.0 1.60 1.0
1N5287 0.297 0.33 0.363 6.6 1.35 1.0
1N5288 0.351 0.39 0.429 4.1 1.00 1.05
1N5289 0.387 0.43 0.473 3.3 0.87 1.05
1N5290 0.423 0.47 0.517 2.7 0.75 1.05
1N5291 0.504 0.56 0.616 1.90 0.56 1.10
1N5292 0.558 0.62 0.682 1.55 0.47 1.13
1N5293 0.612 0.68 0.748 1.35 0.40 1.15
1N5294 0.675 0.75 0.825 1.15 0.335 1.20
1N5295 0.738 0.82 0.902 1.00 0.29 1.25
1N5296 0.819 0.91 1.001 0.88 0.24 1.29
1N5297 0.900 1.00 1.10 0.80 0.205 1.35
1N5298 0.990 1.10 1.21 0.70 0.18 1.40
DO-35 CASE