TRANSITION AND DIFFUSION CAPACITANCE

• In the reverse-bias region we have the transition- or depletion-region capacitance (CT), while in the forward-bias region we have the diffusion (CD) or storage capacitance.
• In the reverse-bias region there is a depletion region (free of carriers) that behaves essentially like an insulator between the layers of opposite charge
• Since the depletion width (d) will increase with increased reverse-bias potential, the resulting transition capacitance will decrease
• Since the depletion width (d) will increase with increased reverse-bias potential, the resulting transition capacitance will decrease
• in forward bias The result is that increased levels of current will result in increased levels of diffusion capacitance
• increased levels of current result in reduced levels of associated resistance (to be demonstrated shortly), and the resulting time constant which is very important in high-speed application