the question is here
https://i40.tinypic.com/2m2flax.gif
when the diode is letting currect flow threw it
we have
V=4e^(-0.5t)+2t+4
when the diode is not letting currect flow threw it
we have
V=2t
what next
??
Hello again,
Since part of the text is missing (that pic cuts off the last part of the text)
i have to guess that they are asking us two questions here:
1. To find the voltage response across the capacitor to a ramp current 'is'
2. To compare the derivative of the result to the current through the capacitor
and decide if the current through the capacitor is really the derivative of the
voltage across it.
In other words, the text would read:
For the circuit shown in Fig P4.24, calculate the ramp response across the capacitor,
that is, the response v due to an input is(t)=r(t) with v(0)=0. Is the cap current
response for the circuit the derivative of the (voltage) ramp response?
If so, then the way to go about it is to first calculate the voltage response as
you already have done (but check your accuracy) and then take the derivative
of that response, call that dv/dt. Then, calculate the current response through
the cap and compare this to the previously calculated dv/dt to see if they are
indeed the same, or different.
The true voltage response is:
v=IS*(4*e^(-0.5*t)+2*t-4)
for 'is' being a ramp r(t)=IS*t.
so you should check your accuracy first, then proceed with the rest.
BTW you should be able to guess the result before you even do any
additional work, but i believe you should verify that too.
Let me know what you come up with ok...
In the future, try to get better pics so parts of the text are not missing.