Okay, this is my first time posting anything so hopefully I get this right:
I've been given the following problem to do. It's a very basic circuit, just an unknown current source in series with a 25 fF capacitor going to ground. The question wants to know how large the current source must be so that the voltage across the cap reaches 0.6V in 30ps. Other than saying it wants the answer in mA, that's all you're given. And frankly, I haven't the slightest idea where to begin...
The focus of the lecture was about how all circuits that contain a single capacitor or inductor have an exponential response vs time. The prof said that the key to remember while doing these problems is the equation t = τ ln(B/A), where B is the value which the exponential is approaching, A is the difference between B and the value of the curve at time t, and τ is the time constant equal to RC. However, I don't know what the voltage across the capacitor is growing to, nor do I have a value for R, so to me this equation doesn't seem to be much help.
If someone could just give me a jumping off point, I'm sure I'd be able to run with it. Am I even on the right track with that formula? Any help would be greatly appreciated. Thanks in advance.
And for good measure, the problem is attached...
I've been given the following problem to do. It's a very basic circuit, just an unknown current source in series with a 25 fF capacitor going to ground. The question wants to know how large the current source must be so that the voltage across the cap reaches 0.6V in 30ps. Other than saying it wants the answer in mA, that's all you're given. And frankly, I haven't the slightest idea where to begin...
The focus of the lecture was about how all circuits that contain a single capacitor or inductor have an exponential response vs time. The prof said that the key to remember while doing these problems is the equation t = τ ln(B/A), where B is the value which the exponential is approaching, A is the difference between B and the value of the curve at time t, and τ is the time constant equal to RC. However, I don't know what the voltage across the capacitor is growing to, nor do I have a value for R, so to me this equation doesn't seem to be much help.
If someone could just give me a jumping off point, I'm sure I'd be able to run with it. Am I even on the right track with that formula? Any help would be greatly appreciated. Thanks in advance.
And for good measure, the problem is attached...
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