PURPOSE: To eliminate an influence of the variance of the element characteristic to detect and amplify an analog signal having a minute amplitude with a high sensitivity by giving a DC potential to the input ends of transistors(TRs) constituting a differential pair through an inductor.

CONSTITUTION: In a differential amplification circuit, load resistances RL are provided on the collector sides of TRs Q5 and Q6 which have emitters connected in common and constitute a differential pair, and the common emitter is connected to an emitter power source VEE through a current source TR Q7. A DC bias potential VR is given to bases of current source TRs Q3, Q4, and Q7 in common. An external power source is used to give a DC potential V0 to bases of the differential pair of TRs Q5 and Q6 through inductors L1 and L2. Consequently, base terminals of the differential pair of TRs Q5 and Q6 are always fixed to the certain potential V0 with respect to DC independently of the variance of characteristics of level shift TRs Q1 and Q2.