| 摘要 |
PURPOSE:To set independently an output bias potential and a gain by applying feedback to an amplifier so that the output bias potential is equal to a potential given optionally. CONSTITUTION:The base potential of both input terminals 10, 16 of a differential amplifier Amp1 is operated to be made equal to a base potential of both input terminals 18, 20 of a differential amplifier Amp2. Even if the level of an output terminal V0 is fluctuated due to a signal, the signal component is cut off by a low pass filter comprising a resistor R3 and a capacitor C so as to make the base of a non-inverting input 18 of the amplifier Amp2 at a constant potential and the output current becomes a constant current. In giving a bias to an input terminal VB1 from an input terminal V1 and to an input terminal VB2 from an inverting input 20 of the amplifier Amp2, the level of a connecting point between resistors R1 and R2 goes to VB1 and the level of a connecting point between the resistor R3 and the capacitor C goes to VB2 so as to set optionally the output bias potential. Thus, the gain and the output bias potential are set independently.
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