| 摘要 |
PURPOSE:To amplify or attenuate the output of a differential connection amplifier during the period corresponding to a control signal, by providing a switching means in the output side of the amplifier and by controlling an input signal of the amplifier by the control signal. CONSTITUTION:When a control signal vc to a terminal 12 is low-level, a transistor TR23 is turned off, and a bias source TR14 is turned on. By setting a large voltage drop due to a resistance 26, a switching TR20 is turned on, and a TR21 is turned off, and all of the current IO of a TR10 for constant current is flowed to the TR20, and only TRs 16 and 17 are operated as a differential amplifier. When collector resistances R8, R9, and RC of the differential amplifier are equal to one another and emitter resistances R10-R13 are equal to an emitter resistance RE, an output voltage vO is equal to (RC/2RE).vi (vi is an input voltage of a terminal 11). When the signal vC is high-level, the TR23 is turned on, and a TR22 is turned off, and TRs 20 and 21 are turned on, and four TRs 16, 17, 18, and 19 are operated as differential amplifiers, and the output voltage vO is equal to RC/REXvi, and thus, the output signal is changed in accordance with the control signal. |
