| 摘要 |
PURPOSE:To eliminate the need for many parts for a compensating circuit and to reduce the size of the whole system by connecting another diode to a diode for detection in series and applying a bias voltage, and generating a voltage corresponding to an offset voltage generated at the input terminal of an operational amplifier and making them cancel each other in case of variation in ambient temperature. CONSTITUTION:Diodes 9 and 10 of the same structure are formed on an integrated circuit board and equal in voltage offset generated when forward biases are supplied through resistances 11 and 12. When the resistances 14 and 15 are equalized in value, on the other hand, the voltage offsets are added mutually by the resistances 14 and 15 about a point (c), so that the voltage offset is zero between (c) and (d). Even if the voltage offset has a drift owing to temperature, the output has no offset voltage through the balance circuit of the resistances 14 and 15 at any time. Thus, the temperature compensation of a rectifying circuit is performed and the influence of the temperature drift upon the voltage offset is eliminated to enable a level detecting circuit to operate at predetermined input level.
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