| 摘要 |
PURPOSE:To attain a big change of gain with a low level of fed power supply voltage by controlling the gain without changing the current flowing to a resistance connected to paired transistor by a current source of a differential amplifier. CONSTITUTION:The emitters of npn transistors (TR) 10 and 11 with their base electrodes connected with each other are grounded through resistances 12 and 13 respectively; while the collectors of the TRs 10 and 11 are connected to the cathodes of diodes 3 and 4 and then to the collectors of the paired TRs 10 and 11. It is possible to control the gain of this amplifier with the collector current I3 of the TRs 10 and 11 respectively. The voltage drops of resistances 6 and 7 can be fixed by fixing a current I1. Thus the changing width of gain can be increased even with a low level of the fed power supply voltage VCC. |
