| 摘要 |
PURPOSE:To obtain a signal selecting circuit without power loss and leakage of a signal and without being injured for frequency characteristics by shunting a base input of a differential pair transistor (TR) and also making a constant current load of an input TR inoperative. CONSTITUTION:When an RF switching pulse serving as a control signal to a TRQ11 is at L level, a Q11 is turned off, TRs Q12, Q13 of the current mirror CM constitution are turned on and a load TRQ9 and a TRQ14 of the CM constitution are turned on. Then a constant current is fed to the 2nd input TRQ3 to attain the normal operating state. Further the 1st input is interrupted by conducting a TRQ5 through the H level base input of the Q13, a TRQ15 is turned on, TRs Q15, Q17 of the CM constitution are turned off, the 1st load TRQ8 and a TRQ18 of the CM constitution are turned off to interrupt the current supply to the 1st input TRQ1. Further a TRQ6 is made nonconductive by the base of the Q17, the 1st input is interrupted completely and only the 2nd input is selected and introduced. When a control signal to the Q11 is inverted, the operation is reversed, the 2nd input is interrupted and only the 1st input is selected. |
