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

comparator hysteresis - help needed

Status
Not open for further replies.
J

Jevon

Newbie level 2
Newbie level 2
Joined
Nov 26, 2009
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
South Africa
Activity points
1,293
comparator hysteresis

Hi all,

I've got a comparator comparing the value from an open collector sensor (pull up to 5V through a 10k) and 2.5V (set up through pot. divider... 2 x 10k res.). I'm getting kick back noise which is a problem because they comparator output (open collector pulled up with a 10k as well) is fed to a counter.
Because of the way the inputs are set up, I'm not sure how to set up feed back to sort out the noise problem.
Suggestions would be great.

Thanks
 

Re: comparator hysteresis

Hi,

If you can make the comparator sluggish by reducing bias current, it can solve the problem. Basically it is slowing down the comparator output.
In case you need very fast response from the comparator, then adding hysteresis can solve the problem.
 

    J

    Jevon

    Points: 2
    Helpful Answer Positive Rating
Re: comparator hysteresis

Jevon said:
Because of the way the inputs are set up, I'm not sure how to set up feed back to sort out the noise problem.
Click to expand...
Both your comparator inputs own an input resistance of 5kΩ. So if you want e.g. a hysteresis of 1% (means 50mV in a 5V system), you use a feedback resistor (to the positive input) of (input_resistance / hysteresis_percentage) value, i.e. 500kΩ in your case.
 

    J

    Jevon

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top