| 摘要 |
PROBLEM TO BE SOLVED: To increase voltage gain while securing high stability. SOLUTION: The calculation amplifier comprises a condenser C21 for coupling an output terminal of a differential amplification circuit 22 connected in a folded-cascade manner and an input terminal of a voltage amplification circuit 24, and a bias setting circuit 23 comprising switches 39, 40. After a bias setting operation for switching a switching signal VINIT to H to charge the condenser C21 with bias voltage, the switching signal VINIT is switched to L to perform an amplification operation. The condenser C21 operates as a level shift circuit to bias the transistors Q27, Q29 so that they operate in a saturation region. With this, an output impedance of the differential amplification circuit 22 is increased, thereby the voltage gain being increased. Since a transistor circuit such as a source follower or the like is not employed for a level shift circuit, high stability is maintained.
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