| 摘要 |
PROBLEM TO BE SOLVED: To provide a logarithmic amplifier by which logarithmic conversion is performed with sufficient precision without depending on base current amplification factorβof a bipolar transistor which performs logarithmic amplification and suitable to an integrated circuit. SOLUTION: In the logarithmic amplifier, voltage-current conversion of input voltage Vin is performed by a circuit constituted of a differential amplifier 1, a resistor R1 and a MOS transistor Q1 and the transformed current is made to flow in a transistor Q3. In addition, a transistor Q2 of the same type as that of the transistor Q3 is serially connected to a reference current source 2. Then, difference voltage between emitter voltage of the transistor Q3 and emitter voltage of the transistor Q2 is taken out as output voltage and the logarithmic amplifier without depending on the base current amplification factorsβof bipolar transistors Q2, Q3 at all is realized. COPYRIGHT: (C)2006,JPO&NCIPI
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