| 摘要 |
PURPOSE:To obtain a double balanced differential amplifier which is effective in a low voltage working mode with an easy design for maximum input of distortionless allowance, by connecting a constant current source between a positive power supply and each common emitter of four transistors connected in terms of a double balanced differential way. CONSTITUTION:Constant current sources 110 and 111 are connected between a positive power supply 109 and a common emitter, and a 1:n emitter area ratio is given between transistors Q15 and Q16 as well as Q17 and Q18 respectively which constitute a current inverting circuit. The emitter currents of the Q8 and Q9 increase with addition of constant current sources. However the working currents of the Q16 and Q18 have no increase. This prevents the decrease of the maximum gain and the increment of the minimum power supply voltage. Furthermore the level of the distortionless allowance input can be set equal to the conventional level, and the minimum current source voltage has no increase either.
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