look in the weidmuller cataloge, or their web site.

also phenex contact makes one too I think

I built one using a PIC feeding PWM into an RC network. Adjust the duty cycle of the PWM output to vary the current. Works great.

1. How pre-cise you need?

2. How large the city/town you are living in? Do you find some Electronic Shops?

If precise source is needed, then look for vendors as suggested by one gentle-man, add RS Components [UK] & Farnels[UK] or its local agent.

If just for experiments purpose, then I suggest to use a 3terminal Fixed 5V reg [min I ratings].

1.) Connect a resistor of 50K 1/4w between O/P terminal & Com.

Combination of 4K7 & 500R in series is preferred for some adjustments to more accurate values.

2.) Connect Com terminal to I/P of your Cct's I/P point for

constant Source.

3.)Apply at least +12V to I/p Terminal of Regulator . Keep in mind the I/P wkg voltage of Regulator.

Sorry for error read "5K" for "50K"

For 2/3 terminal precision CCS [Constant Current Source] contact in Bharat:

RS Components & Controls (India) Ltd

44 Okhla Estate

New Delhi - 110 020, India

Tel: 91 11 6326991/2

Fax: 91 11 6326993

www.rsindia.com

If you do not need high precision you can use a single JFET transistor with a resistor in series with the source and the gate connected to the low end of the resistor. The voltage developed in the resistor from current flow will reverse bias the gate and the regulation is not too bad for a lot of uses. Such devices as a 2N5457 are common and adequate for many applications.

I need constant DC 1mA current source for one application.Can u give any circuit diagram with explanation.Is it available any device which will give 1ma o/p without external circuit.

ANEESH V S

DRDO, INDIA

Have you gone to www.globalspec.com? They may give some equipment.

Simple Emitter follower-1 humble NPN transistor with high beta+ a few half watt resistors from a 6Volt battery.

Two diodes in series, anode to base, cathode to ground. Six hundred ohm quarter watt resistor from emitter to ground. Ten thousand ohm quarter watt resistor from base to plus 10 volts. Transistor (NPN) collector will sink ~ 1ma to ground. Apply load between positive supply and collector. If you need to source the current use PNP and flip "ground" and plus.

Another "Brute force and sheer ignorance" circuit will be:

330 VDC (easy to get from line 240VAC through a half-wave rectifier diode +Elcap) leaking to ground thro' 3x 100kOhm 1 watt resistor in series to a Zener diode -say 10-15V to ground . At this junction connect your famous DRDO load thru' milliammeter 0-2ma range( orDVM).Also at this junction you join a trimming Pot( as a resistance) say 200 Kohm to Ground. Connect your famous DRDO 1ma load from this junction to ground and fly to the moon.

A LM334 or similar part will give you a 2 terminal constant current source with a single resistor. It's a common National Semi part and several manufactures make a similar constant current source.

There are true two terminal devices that can limit current. I am not sure about product availability.

http://www.allaboutcircuits.com/vol_3/chpt_3/16.html

Our company sells an adaptor device that plugs onto a PCMCIA card, and provides 2 ma constant current from a 24 volt source into a 500 ohm load. (This provides a 10 volt bias level.) There are also battery operated or 110 volt 50/60 cycle 24 volt 2 ma power supplys that provide 2 ma. Most of these can easily be converted to 1 ma. Perhaps you can provide more information on your application. JEJ

Use a J505 (20%) or a CR100 (if they still exist). Or use the circuit above:

The 5.6 V zener minus the 0.6 V drop across the base emitter sets the voltage across R1 at 5V. Tweak the components to get the exact value for your application.

hello sir

can u give me more information about these ckts. i want 1 or 2 ma constnat current from a source which have the voltage range of 3 to 6 volt.

thanx

Hello Aneeessh,

Linear Integrated Systems manufactures a two-terminal, current-regulating device (J500 Series) which requires no external components. Depending on the particular model, the device can supply anywhere from 0.24 to 4.7 mA. Their 1 mA version is the J505.

Linear Integrated Systems
4042 Clipper Court
Fremont, California 94538-6540
Web Site: http://www.linearsystems.com
Phone: 510-490-9160
Fax: 510-353-0261

-e

At $4.75 EA Sheeeesh!