| 摘要 |
PURPOSE:To reduce the collector loss of each amplifier to almost the same value and to realize high efficiency and size reduction by switching plural power sources fast according to the amplitude of an input signal and applying a specific potential to respective amplifiers. CONSTITUTION:When the input signal rises until the output signal level at a point P exceeds a reference value + or -V1, a driving signal of a driving circuit 9 based upon the control signal (SCA) from a level detecting circuit 8 closes a switch S1, opens an S2, and leaves an S3 closed. Therefore, such an output signal S0 that V2>S0>=V1 appears at an output terminal 7 through TRs 5 and 6, and Q4 and Q7. When the input signal further rises until the signal level at the point P exceeds a reference voltage + or -V2, a driving signal is generated on the basis of a control signal (SCB) to open the switch S3 and close the S2 and S1, so that the output signals S0 substantially within the range of VC>S0>=V1 is generated through TRs Q3 and Q8. When the input signal decreases, similar operation is performed to switch power sources successively according to the level of the input signal. |
