What happens to the capacitance when voltage is increased?

[663697]

According to C = Q/V the capacitance should increase when the voltage is decreased, or when the charge is increased. I got a question wrong on EK where the equation C = (k *E*A)/L was given for the capacitance (where E is the permittivity of free space), and it presented a voltage clamp experiment that was done. The question asked what was the purpose of using a large voltage for the voltage clamps, and the explanation says that the capacitance of the membrane is only dependent on the physical characteristics of "A" and "L". Am I missing a key concept here? Why wouldn't a change in membrane potential affect the membrane capacitance?

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[aldol16]

It's using a voltage clamp right? The point of a voltage clamp is to hold the voltage constant - if the voltage is constant, then there capacitance no longer depends on voltage.