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Wenye
Joined: 21 May 2003
Posts: 32
Helped: 1
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 23 Jan 2004 15:24 Slew rate control |
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Hi All,
Does anyone has idea in adjustable slew rate circuit.
I need a circuit that can adjust slew rate of rising and falling edge separately. And the adjustable rate from 1ns to 100ns in 0.5 or 1ns per step.
Does anyone has any idea ?
Thank you in advance!
Wenye
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electronrancher
Joined: 24 Mar 2002
Posts: 505
Helped: 34
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| 24 Jan 2004 5:46 |
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yup - use a current source, and increase the current for faster slew. Anytime you mess with slew, you gotta know the capacitance on the output. (whatever node is slewing)
If you don't know the capacitance, you gotta add a cap big enough to be the main event (maybe 100pf if you expect to drive a bunch of logic gates, but dunno how many)
now compute slew with I=C(dV/dT). You wanna slew your 100pf from 0-5v in 100ns? -> 5mA.
10ns? 50mA
1ns? 500mA
0-1v in 1ns? 100mA
0-15v in 10ps? 150A. This gets tough up here.
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Wenye
Joined: 21 May 2003
Posts: 32
Helped: 1
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24 Jan 2004 16:29 Re: Slew rate control |
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Hi Electronrancher,
First, thank you for your reply.
U idea is right and heuristic... Load capacitance (include pcb distributed capacitance) is around 50pF. But as my knowledge to drive a current source which is run in very high speed ( setting time of output current is lower then 1ns ) is a very difficult job.
Could u pls give me any idea how to do...
Wenye
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radix
Joined: 23 Jul 2002
Posts: 157
Helped: 5
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26 Jan 2004 17:55 Re: Slew rate control |
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Wenye,
What's your application and technology(cmos, bipolar, etc...)?
Even though you say analog circuit design I've seen people call designing cmos output drivers "analog design".
Radix
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26 Jan 2004 17:55 Ads |
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airace
Joined: 17 Sep 2002
Posts: 97
Location: Deep in a chip
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28 Jan 2004 11:05 Re: Slew rate control |
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This paper may be of help to you...
it is on a idea for a o/p buffer with adaptive slew control
mechanism
regards
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tlbb
Joined: 13 Feb 2004
Posts: 9
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02 Mar 2004 7:10 Re: Slew rate control |
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Usually I/O circuits has slew rate requirement. Check those reference.
Basic ESD and I/O Design
by Sanjay Dabral (Author), Timothy Maloney (Author)
has some sample circuits.
Basic ESD and I/O Design
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mukeshk
Joined: 15 Jun 2004
Posts: 11
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16 Jun 2004 13:49 Re: Slew rate control |
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Look for source cross coupled opamp topology..
Here u can control the positive and negative slew rates seperately..
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alphi
Joined: 23 Dec 2001
Posts: 440
Helped: 1
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16 Jun 2004 16:41 Re: Slew rate control |
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hi,mukeshk
can you supply some articles about"source cross coupled opamp topology"
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opamp741
Joined: 17 Jun 2004
Posts: 145
Helped: 10
Location: India
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17 Jun 2004 21:25 Re: Slew rate control |
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Check page no 390 of Allen Holberg..
Update me with ur status..
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opamp741
Joined: 17 Jun 2004
Posts: 145
Helped: 10
Location: India
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17 Jun 2004 21:27 Re: Slew rate control |
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Check page no 390 of Allen Holberg..
Update me with ur status..
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opamp741
Joined: 17 Jun 2004
Posts: 145
Helped: 10
Location: India
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17 Jun 2004 21:28 Re: Slew rate control |
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Check page no 390 of Allen Holberg..
Update me with ur status..
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alphi
Joined: 23 Dec 2001
Posts: 440
Helped: 1
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18 Jun 2004 2:31 Re: Slew rate control |
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| do you use it for electronic load?
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opamp741
Joined: 17 Jun 2004
Posts: 145
Helped: 10
Location: India
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20 Jun 2004 6:59 Re: Slew rate control |
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| Ur question is not clear..Or may be lack of knowledge at my side..
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