| 摘要 |
PURPOSE:To execute stable actions in case of making it an IC by setting the offset voltage of a comparison circuit for generating an AGC signal according to the voltage between the base and the emitter of a detection transistor. CONSTITUTION:The DC voltage of the output end of an IF amplification circuit 24 is set in a value obtained by level-shifting a power source voltage VCC in a first level shift circuit 28 and the DC voltage of one input of the comparison circuit 32 becomes equal to the DC voltage of the output end of the IF amplification circuit 24. Supposing that the number of diodes which constitutes the first level shift circuit 28 is n1, the DC voltage in one input of the comparison circuit 32 becomes VCC-n1VBE. And supposing that the number of the diodes which constitutes a second level shift circuit 33 is n2, a reference voltage impressed on other input of the comparison circuit 32 becomes VCC -n2VBE. Since the offset voltage VS of the comparison circuit 32 is (n2-n1)VBE and it is set only by the number of the diodes and the forward voltage of the diode the offset voltage VS can be stably set in the IC.
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