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CHALLENGE QUESTION TWO
Posted:
Jul 19, 1996 2:44 AM


HERE IS A CHALLENGE DESIGN QUESTION. ANYONE WITH A GOOD WORKABLE SOLUTION WILL BE WELL REWARDED. PLEASE RESPOND DIRECTLY TO ME VIA EMAIL, AND PERHAPS ALSO WITH A POST
I have the following circuit:
(Switched Voltage) VS  R1  ++ (Output) VO   C R3   ++  (Ground)
The switched voltage VS is alternated between a reference, VR, and ground. When switched to VS, the circuit charges C and VO rises. When VO reaches 2/3 of VR, the circuit is automatically switched to ground and begins to discharge C. When C reaches 1/3 of VR, the circuit is automatically switched back to VR and the cycle repeats.
The objective is to determine the value that VO would reach when VS is switched to VR and C is missing (same as if infinite time has passed). Unfortunately, this value can not be measured directly. Instead, I can only measure the time that it takes for VO to independently charge or discharge between 1/3 and 2/3 of VR (VR known if necessary).
Assume that the values of R1 and R3 are such that VO actually reaches 2/3 of VR, and in a quick time frame.
Approximations must be proven to be within better than 0.1%, otherwise they should be avoided.



