| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a variable gain differential amplifier circuit that enables a variable gain while ensuring a wide dynamic range. <P>SOLUTION: A variable gain differential amplifier circuit 12 that has differential amplifier circuits 17; 21 including differential pair transistors Q<SB POS="POST">1</SB>, Q<SB POS="POST">2</SB>; Q<SB POS="POST">3</SB>, Q<SB POS="POST">4</SB>, load resistances 14, 15; 18, 19 connected to respective collectors of the transistors, and current sources 16; 20 connected to emitters of the transistors in common, respectively, and that feeds back an output of the latter stage differential amplifier circuit 21 to the initial stage differential amplifier circuit 17 via feedback transistors Q<SB POS="POST">5</SB>, Q<SB POS="POST">6</SB>includes: a current branch circuit section 12C for dividing a current to be applied to the initial stage differentia pair transistors Q<SB POS="POST">1</SB>, Q<SB POS="POST">2</SB>; and a current supply circuit section 12B for supplying a current to the differential pair transistors Q<SB POS="POST">1</SB>, Q<SB POS="POST">2</SB>. <P>COPYRIGHT: (C)2012,JPO&INPIT |
