| 摘要 |
PURPOSE: A high power amplification circuit for a cellular phone is provided, which includes a protection circuit to prevent a power transistor from being damaged according to an excessive input bias increase due to an auto gain control circuit(AGC) when a signal from the external is in a low power state. CONSTITUTION: An amplification part(31) amplifies a power of a signal inputted from the external, and a signal applying part(32) couples a signal and applies it to the amplification part. A bias part(33) applies a bias to the amplification part. A power supply part(34) supplies to a power supply voltage to the amplification part. An amplification protection part(36) is connected to the signal applying part and the bias part electrically and prevents the amplification part from being damaged according to an increase of the bias due to an auto gain control circuit(AGC)(35) when the input of the external signal is blocked. An impedance matching part(37) matches an impedance of the amplification part with an impedance toward a next stage from the amplification part. A directional coupler(38) judges a matching with an antennal by detecting a reverse intensity of the signal amplified in the amplification part and then determines whether to transmit a signal output. And a signal output part(39) outputs a signal.
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