| 摘要 |
A PIN diode attenuator and associated control circuits prevents self-biasing of bipolar device RF power amplifiers under large signal drive conditions. A power amplifier control signal controls the amount of current through the PIN diode attenuator. When the control signal is high for maximum output power, the PIN diode attenuator is turned off to obtain maximum drive level for the first RF stage. When the control signal is low for maximum isolation, the PIN diode attenuator is turned on to reduce the drive level and to avoid self-biasing. The PIN diode attenuator and associated control circuits allow the RF power amplifier to operate normally when the amplifier is in its forward gain mode. The RF input signals to the power amplifier are attenuated however, when the amplifier is turned off or in a transition state between the forward gain mode and the off mode, to ensure a high isolation state that prevents self-biasing of the power amplifier or portions thereof under large signal conditions.
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