| 摘要 |
A radio receiver-transmitter apparatus equipped with a signal changeover switch which is capable of properly dealing with a high-power radio frequency signal and ensuring a desired insertion loss and superior isolation characteristic. The switch has a signal input terminal (12/22), a signal output terminal (14/24) and a signal input-output terminal (11/21), and comprises a 1st FET unit (15/25) connected to the input terminal (12/22) and the input-output terminal (11/21), a 2nd FET unit (16/26) connected to the input terminal (12/22) and the ground, a 3rd FET unit (18/28) connected to the output terminal (14/24) and the input-output terminal (11/21), and a 4th FET unit (17/27) connected to the output terminal (14/24) and the ground. The gate width of each transistor in the 1st FET unit (15/25) is so determined as to render the source-drain saturation current greater than the maximum current amplitude of the input signal fed from the input terminal, and each of the 2nd and 3rd FET units (16,18/26,28) consists of one or more transistor stages equal in number to the result of rounding up the numerical value which is obtained by dividing the maximum voltage amplitude of the input signal fed from the signal input terminal, by the withstand voltage of the transistors in the 2nd and 3rd FET units. <IMAGE> |
