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

the role of resistor

Status
Not open for further replies.
A

akbarza

Full Member level 2
Full Member level 2
Joined
Dec 18, 2013
Messages
131
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,296
Activity points
2,556
hi
please note to attached file.
1) what is the role of R1 resistor and why this value is selected for it?
2) for opamp, there are restiction as slew rate and gbw(gain band width) and noise. for a special signal career and data ( their frequency and amplitudes),what limits are settle on opamp?
namely for supposed f_carrier and f_data, what must be gbw of opamp?
for supposed amplitude of data signal, what must be slew rate of opamp?
thanks
 

Attachments

  • image1.pdf
    145.4 KB · Views: 160

Sort by date Sort by votes
Circuit makes no sense. You've got an UNDEFINED op amp with no feedback. No way of knowing what the resistor is for without knowing what the op amp is. Running an opamp open loop is never a good thing.
 

Upvote 0 Downvote
Hi,

Opamp and comparator sadly share the same symbol. But they are different.
I guess initially the schematic used a comparator, which needs a pullup.
But then some one decided to misuse an Opamp as comparator but missed to remove the pullup (an Opamp needs no pullup)

Klaus
 

Upvote 0 Downvote
barry said:
Circuit makes no sense. You've got an UNDEFINED op amp with no feedback. No way of knowing what the resistor is for without knowing what the op amp is. Running an opamp open loop is never a good thing.
Click to expand...
this circuit is used to create zero and one( in digital domain) as zero volt and 5 volt.
in open loop amplifier it goes to saturation( ideally to vcc or vee), so here an open loop amplifier has been used.
 

Upvote 0 Downvote
Hi,

if you want digital output (saturated): then use a comparator
if you want analog output (non saturated) then use an OPAMP

that´s why they designed two different devices.

Klaus
 
Upvote 0 Downvote
R1 is used for open collector comparator circuits, which allows them to
achieve high level output.

If used on an OpAmp results device dependent, eg. output driver structure.

Other conbsiderations :

1659006340505.png


Other considerations :

Activity: The Comparator, Positive Feedback and Schmitt Trigger, For ADALM1000 [Analog Devices Wiki]

wiki.analog.com wiki.analog.com


Your circuit, weather it be OpAmp or Comparatoir based, should have some + fdbk to
eliminate false triggers due to noise.





Regards, Dana.
--- Updated ---

2) for opamp, there are restiction as slew rate and gbw(gain band width) and noise. for a special signal career and data ( their frequency and amplitudes),what limits are settle on opamp?
namely for supposed f_carrier and f_data, what must be gbw of opamp?
for supposed amplitude of data signal, what must be slew rate of opamp?
thanks
Click to expand...

Basically think of a period you need, eq at highest data rate. Then decide on what
percentage of period you can live with eaten up by OpAmp/Comparator response
time. I am not a designer in this topic but would think 10% of period for settling
(=90% legit usable pulse) makes sense. Then you can can look at how much time
it takes to settle, the rest must be allocated to slew rate. And then do that simple
calculation.

Note receiver side has min specs it needs, so that drives the design of Tx side.


Regards, Dana.
 
Last edited:
Upvote 0 Downvote
danadakk said:
R1 is used for open collector comparator circuits, which allows them to
achieve high level output.

If used on an OpAmp results device dependent, eg. output driver structure.

Other conbsiderations :

View attachment 177715

Other considerations :

Activity: The Comparator, Positive Feedback and Schmitt Trigger, For ADALM1000 [Analog Devices Wiki]

wiki.analog.com wiki.analog.com


Your circuit, weather it be OpAmp or Comparatoir based, should have some + fdbk to
eliminate false triggers due to noise.





Regards, Dana.
--- Updated ---



Basically think of a period you need, eq at highest data rate. Then decide on what
percentage of period you can live with eaten up by OpAmp/Comparator response
time. I am not a designer in this topic but would think 10% of period for settling
(=90% legit usable pulse) makes sense. Then you can can look at how much time
it takes to settle, the rest must be allocated to slew rate. And then do that simple
calculation.

Note receiver side has min specs it needs, so that drives the design of Tx side.


Regards, Dana.
Click to expand...
--- Updated ---

hi danadakk
can i ask you what is reference of attached text by you?( i mean 4.8 using opamp as comperator)
thanks
--- Updated ---

hi danaddk
thanks for respond
can i ask you what is reference or main text of "4.8 using opamp as comparator"
i am not familiar with open collector comparator circuits. what are they?
thanks again.
 
Last edited:

Upvote 0 Downvote
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top