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.

How do we measure slew rate of opamp in Cadence!!

Status
Not open for further replies.

Anachip

Member level 2
Joined
May 28, 2005
Messages
45
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
1,766
slew rate of op amp

Hi Guys,

I like to know, how do we measure slew rate of an opamp in cadence.

What is the relation of slew rate and settling time.

Thanks
 

OpAmp

Member level 3
Joined
May 19, 2003
Messages
60
Helped
19
Reputation
38
Reaction score
5
Trophy points
1,288
Activity points
693
slew rate cadence

Hi,

Measuring the slew rate in Cadence is similar to measuring it in other simulator. Close the feedback loop of the op-amp and apply a large step voltage to the input of the op amp, and measure the initial slope of the output.

There is not a close relation between slew rate and settling time of an op-amp. Some you can increase the slew rate of an op amp using a nonlinear circuit wile the circuit doesn’t have any effect on the settling time.

Following IEEE papers are helpful to read:

“Relationship between frequency response and settling time of operational amplifiers”
Kamath, BYT; Meyer, RG; Gray, PR.
IEEE JSSC’74

"Analysis of the settling behavior of an operational amplifier"
Chuang, C.T.;
IEEE JSSC’82
 

suria3

Full Member level 5
Joined
Mar 5, 2004
Messages
304
Helped
17
Reputation
34
Reaction score
5
Trophy points
1,298
Activity points
3,042
op amp slew rate

Hi Opamp,

Can u upload the paper you mentioned here.

Regards,
Suria
 

Anachip

Member level 2
Joined
May 28, 2005
Messages
45
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
1,766
how to measure slew rate

OpAmp said:
Hi,

Measuring the slew rate in Cadence is similar to measuring it in other simulator. Close the feedback loop of the op-amp and apply a large step voltage to the input of the op amp, and measure the initial slope of the output.

There is not a close relation between slew rate and settling time of an op-amp. Some you can increase the slew rate of an op amp using a nonlinear circuit wile the circuit doesn’t have any effect on the settling time.

Following IEEE papers are helpful to read:

“Relationship between frequency response and settling time of operational amplifiers”
Kamath, BYT; Meyer, RG; Gray, PR.


IEEE JSSC’74

"Analysis of the settling behavior of an operational amplifier"
Chuang, C.T.;
IEEE JSSC’82

hi opamp, this is the first time im measuring the slew rate in the eda tool like cadence. As you said, the opamp as close loop, now it is like a unity gain buffer. I dont get about the "large step voltage" and the slope u mentioned. Please explain me clearly.
 

c_m_o_s

Newbie level 6
Joined
Jul 27, 2004
Messages
12
Helped
3
Reputation
6
Reaction score
1
Trophy points
1,283
Activity points
128
measuring slew rate

run a transient analysis by giving a large voltage step at the input (rail to rail) to take the opamp in non linear mode of operation, measure the slope of the ouput waveform..that'll give you your slew rate.
 

huojinsi

Full Member level 5
Joined
Jan 21, 2005
Messages
256
Helped
25
Reputation
50
Reaction score
6
Trophy points
1,298
Activity points
2,216
measure slew rate

What is the relation of slew rate and settling time.
Settling time is electrical parameter of opa under small signal, but the slew rate is electrical parameter of opa under large signal. I think they both have no relation.

When simulating in cadence, connect out of the opa to the inverter "-", make sure the opa is a follower. put a large pulse signal to the noninverter "+" terminal and do transient analysis, then plot the out wave(of course,under the load u defined). at last, measure the slope of out voltage linear ramp, it is slew rate.

Pls correct me if i am wrong!
 

    Anachip

    Points: 2
    Helpful Answer Positive Rating

OpAmp

Member level 3
Joined
May 19, 2003
Messages
60
Helped
19
Reputation
38
Reaction score
5
Trophy points
1,288
Activity points
693
slew rate measure

Hi guys,

Sorry for being late for your replying for questions, but, fortunately, huojinsi explained it very well. Just to add something to huojinsi, usually if we don’t use a nonlinear circuit for enhancing the SR of an opamp, a high SR opamp has also fast small signal responce. For example, when output load is small and the current in the opamp’s braches are high, the opamp has both fast small and large signal responses.

OpAmp
 

Anachip

Member level 2
Joined
May 28, 2005
Messages
45
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
1,766
how to measure slew rate

A big thanks to Huojinsi and Opamp. i got the answer ready.
 

Jim cage

Full Member level 3
Joined
Jul 2, 2006
Messages
150
Helped
13
Reputation
26
Reaction score
7
Trophy points
1,298
Activity points
2,175
amp measure settling time

Make sure that you have only dc connection in the loop for biasing when you measure the slew rate. usually, you connect an Inductor in the feedback path to have a dc biasing and to exclude AC signal on this path.
 

layes2

Full Member level 4
Joined
Dec 3, 2004
Messages
230
Helped
10
Reputation
20
Reaction score
6
Trophy points
1,298
Activity points
1,410
how to measure the slew rate

dv/dt use calculator
 

mba7

Newbie level 6
Joined
Feb 27, 2006
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,335
cadence slew rate

good paper

any other papers about simulating op amp
 

vepsbeoriginal

Newbie level 1
Joined
Mar 11, 2013
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,285
Re: how to measure slew rate

brother plz plz plz tell me how to see slew rate of an op amp. if anyone has circuit which is working in cadence, plz give me link or upload it or mail me..
i am very week student, i hv final year project regarding slew rate enhancement.
help me
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top