Variable gain differential amplifier circuit diagram A709

Posted on Mar 28, 2007

As shown for the configuration of the variable gain A709 differential amplifier circuit. The biggest advantage of the circuit is in keeping CMRR KCMR same premise, continuously

Variable gain differential amplifier circuit diagram A709
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adjustable differential gain can be achieved. Circuit four resistors R2 and two resistors R1 resistance must be equal, respectively, the numerical figure shows the typical application time. Adjust potentiometer R3, can realize continuous adjustment voltage magnification. If the adjusted gain adjustment resistor R3 5, the corresponding ratio R2/R3 104, where the voltage amplification Av -104 (2R2/R1), the adjustment range of the apparent gain of the circuit is very wide and easy adjustment. It needs to be emphasized that: the voltage gain is not too large, because when the gain is large Vo near the power supply voltage, the output voltage will be a serious nonlinear distortion. In addition, the introduction of a RC between pin 1,8 compensation branch, between pins 5 and 6 also introduces a compensation capacitor C2, to improve the stability of the circuit, to prevent parasitic oscillation. The basic relationship of the circuit is: Vo - (2R2/R1) (1 + R2/R3) (Vi1-Vi2) Av Vo/(Vi1 a Vi2) - (2R2/R1) (1 + R2/R3) When R1 10k, R2 50k, R3 5k when, Av -110. A709 integrated chip electrical parameters (VD 15V, TA 25 )

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