The PIN diode must be forward biased (Low Loss or ON State) so that the stored charge, Qs, is much larger than the RF induced charge that is added or removed from the I-region cyclically by the RF current.

This relationship is shown by the inequality: Qs >> Irf / (2*Pi*F)

Storage charge can be evaluated as Qs = If*tau

So, a diode behaves in PIN mode operation if F>>Irf/If *1/(2*Pi*tau) [1]

Below the transit time frequency of the I-region, the PIN diode behaves as a PN junction diode, ie, it rectifies the RF voltage.

Qs stored charge If = Forward Bias Current Irf = rf signal current tau = Minority Carrier Lifetime

BAP55LX has tau = 0.27us thus using equation [1]: F >> 0.6MHz *Irf/If

Low frequency range depends on the RF and bias currents but rough estimation is F>6 MHz. So, this device can be used as RF switch/attenuator at frequencies above few MHz.

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The PIN diode must be forward biased (Low Loss or ON State) so that the stored charge, Qs, is much larger than the RF induced charge that is added or removed from the I-region cyclically by the RF current.

This relationship is shown by the inequality: Qs >> Irf / (2*Pi*F)

Storage charge can be evaluated as Qs = If*tau

So, a diode behaves in PIN mode operation if F>>Irf/If *1/(2*Pi*tau) [1]

Below the transit time frequency of the I-region, the PIN diode behaves as a PN junction diode, ie, it rectifies the RF voltage.

Qs stored charge

If = Forward Bias Current

Irf = rf signal current

tau = Minority Carrier Lifetime

BAP55LX has tau = 0.27us thus using equation [1]: F >> 0.6MHz *Irf/If

Low frequency range depends on the RF and bias currents but rough estimation is F>6 MHz.

So, this device can be used as RF switch/attenuator at frequencies above few MHz.

Reference document "THE PIN DIODE CIRCUIT DESIGNER'S HANDBOOK":

https://ieee.li/pdf/essay/pin_diode_handbook.pdf

Have a great day,

Pavel

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Note: If this post answers your question, please click the Correct Answer button. Thank you!

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