Given that CD at forward current of 1 mA is 0.8 µF, its

Given that C_D at forward current of 1 mA is 0.8 µF, its value for a current of 4 mA is—

We know that diffusion capacitance C_D is given by relation

C_D =	τ·1
	η – V_T

where, I is the forward current.
i.e. CD ∝ I

or		C_D1	=	I₁
		C_D2		I₂

C_D2 =		I₂·C_D1	=	4 × 8µF	3.2 µF
		I₁		1