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

how this channel leakage generated?

Status
Not open for further replies.

lhlbluesky

Banned
Joined
Mar 30, 2007
Messages
558
Helped
5
Reputation
10
Reaction score
5
Trophy points
1,298
Location
china
Activity points
0
in the following picture, the schematic is a part of an ir receiver, here is a twin-t notch filter and a non-inverting amplifier.
in the notch filter, R is programmable (s[2:0]), and switch here is nmos transistor (having body effect), when simulation(assuming s[2:0]=100), in some corner, the leakage current of s[2] is 25nA also, causing a voltage drop of 10mv between VI and non-inverting input of opamp of notch filter; while in other corner, the leakage current of s[2] is only 20pA (what i expected).
i checked the operating point, the leakage current of s[2] is not substrate leakage, it is channel leakage between source and drain. and if i disconnect the output of notch filter with input of the non-inverting amplifier (VR is reference voltage from bandgap), the above leakage current of s[2] can be 20pA~50pA for all corners, as i expected. this is very strange. i wonder why.
how is the channel leakage current of s[2] generated? or is it gate leakage of input pair of notch filter opamp?
please give me some suggestions, thanks all.
2.jpg
 

dick_freebird

Advanced Member level 5
Joined
Mar 4, 2008
Messages
7,029
Helped
2,055
Reputation
4,114
Reaction score
1,901
Trophy points
1,393
Location
USA
Activity points
56,341
When you say "in some corner", is that "model world"
or "real world"? A model that attempts to represent
the worst case leakage floor might, well, leak. I'd say
the first thing to do is visit that corner and take some
classical I-V curves in simulation, looking for differences
against nominal particularly.

Then you can decide whether you are fighting a fiction
or a yet-unencountered production reality.
 

lhlbluesky

Banned
Joined
Mar 30, 2007
Messages
558
Helped
5
Reputation
10
Reaction score
5
Trophy points
1,298
Location
china
Activity points
0
"in some corner" is in "model world", such as tt/3.3/25deg, tt/3.3/85deg (normal: tt/3.0/25deg). and i'm also confused why leakage current is related to the loadind of notch filter, the loading is connected with inverting-end of notch filter opamp, while channel leakage occurs in non-inverting-end of notch filter opamp.
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top