| 摘要 |
PURPOSE:To obtain the output control characteristics of an A-type or C-type volume, by using a B-type volume which is easy to produce. CONSTITUTION:The joint potential between resistances R1 and R2 is set at Va; the joint potential between resistances R2 and R3 is set at Vb; and the joint potential between resistances R3 and R4 is set at Vc respecrively. Then the potential of a mobile terminal 1 of a variable resistance R16 is varied from 0 through VCC. Thus a circuit part comprising transistors (TR)Q5-Q8, resistances R9 and R10 plus a constant current source I3 is actuated with the potential of the terminal 1 set about Vc to obtain the output control characteristics (C). A circuit part comprising TRs Q3, Q4, Q7 and Q8, resistances R7 and R8 plus a constant current source I2 is actuated at the potential of about Vb to obtain the output control characteristics (B). Furthermore a circuit part comprising TRs Q1, Q2, Q7 and Q8, resistances R5 and R6 plus a constant current source I1 is actuated at the potential of about Va to obtain the output control characteristics (A) respectively. |
