Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

current source design

Status
Not open for further replies.

artem

Advanced Member level 4
Joined
May 22, 2003
Messages
1,350
Helped
126
Reputation
252
Reaction score
32
Trophy points
1,328
Location
Turkey
Activity points
13,461
This is challenge question to me , so may be you guys can help.

I am in need of current source with following characteristics :

- fixed current 5 - 10 mA
- power supply range 2 -3 V
- keep working when minimal voltage drop is (across current source) down to 200 mV ( this requirement is most important)
- simple, constituting up to 2 transistors and passives
- current accuracy no worser than 20 % over power supply and temperature (-25 +75) ranges
- does not need tuning at production time
- does not need components selection( let say CMOS transistors for strict V
thgs)
- price no more 5 cent


This current source is needed to keep LED current permanent regardless of power supply and temperature to get stable connection over the optical fiber loop. That is why i need low dropout when voltage on supply is about 2 V and closed to LED's forward voltage.

I proposed solution in another way(using feedback through fiber optical loop) and dont think that it is an elegant, other variants are component consuming or do not comply with some of the requirements .

Thanks in advance

P.S. Yet it shoud also be economic and does not consume more than 50 percent of current going to load
 

sunking

Advanced Member level 3
Joined
May 25, 2004
Messages
874
Helped
70
Reputation
140
Reaction score
23
Trophy points
1,298
Activity points
6,283
delta Vbe/R1 + Vbe/R2
output use cascode
 

artem

Advanced Member level 4
Joined
May 22, 2003
Messages
1,350
Helped
126
Reputation
252
Reaction score
32
Trophy points
1,328
Location
Turkey
Activity points
13,461
cascode ?? But what is minimum voltage drop (i need as low as 200 mV) if there will be 2 transistors in chain ?
May b1e i talk about different thing . Please link to reference or explanation.
Thanks
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top