| 摘要 |
PURPOSE:To avoid the overload state of a transistor (TR) by providing a current bypass circuit between TRs constituting a current mirror circuit. CONSTITUTION:A current I0 of a constant current source CCS set optionally is fed to a TR Q3 via a current bypass circuit E from the current mirror circuit consisting of TRs Q1, Q2. thus, a current I2 fed to a TR Q3 is expressed as I2=I0-I1 (where I1 is a current supplied from the current bypass circuit E). Even when the current I0 of the constant current source CCS set optionally is in overload state, the current I2 fed to the TR Q3 is limited by the current I1 supplied from the current bypass circuit E, the overload state of the TRs Q3, Q4, Q7 is avoided. Further, each current mirror circuit comprising respectively TRs Q5, Q6 and TRs Q8, Q9 is shut surely at the same time.
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