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Design >> Analog Design >> calculating rise time of RC
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Message started by singh on May 23^rd, 2012, 6:38am

Title: calculating rise time of RC
Post by singh on May 23^rd, 2012, 6:38am

i know this is stupid question, but is the rise time for attached circuit tau = RC?

Title: Re: calculating rise time of RC
Post by Vladislav D on May 24^th, 2012, 12:33pm

VDD/(RC) while Voltage drop on R >> Voltage drop on C

Title: Re: calculating rise time of RC
Post by loose-electron on May 24^th, 2012, 1:23pm

http://www.tpub.com/neets/book2/3d.htm

Title: Re: calculating rise time of RC
Post by pixel on May 25^th, 2012, 12:33am

Here is the equation for time T in which voltage changes its value from value V(t=0) to V(t=T).

T=RC*ln((V(cap=open)-V(t=0))/( V(cap=open)-V(t=T)))

If you need rise time form 10% to 90% for step of height V1.
V(cap=open)=V1
V(t=0)=0.1*V1
V(t=T)=0.9*V1

Tr=RCln(0.9/0.1):
Tr=2.19*RC=4.39ms

Title: Re: calculating rise time of RC
Post by Vladislav D on May 25^th, 2012, 7:59am

ups... was reading one thing and was thinking about another :-[