Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics 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

a problem about reference current source

Status
Not open for further replies.
S

superleaf

Junior Member level 3
Junior Member level 3
Joined
May 5, 2011
Messages
30
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Location
HongKong
Activity points
1,539
some paper refers about this kind of reference current source ,they say that Vref is equal to the voltage of source terminal of M62,thus the current draws through the mos M62 will be :Id=Vref/R13,however,using the spectre simulaltion,i can't get this result,actually,i do not understand the principle of this kind of reference current source,could anyone explain it for me?thank you in advanced~~ 未命名.jpg
 

When the opamp feedback is working, the inputs ill be in virtual short, ie source of m62 is vref.
if things are not working, then opamp is not in feedback.

Is vref within the common mode input?
Can the opamp output swing support vref+vgs(m62)?
Do you have enough headroom for vref+vdsat(m62)+vgs(m63)?
 
Hi superleaf,

please add a schematic including the operation point of the internal circuitry of the opamp. You can do this by annotate operation point and voltage in ADE.

Because of feedback the voltage on inverting input node is equal to Vref. So voltage drop at R13 is also Vref. This sets the reference current in the pmos current mirror.
 
Last edited:
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top