| 摘要 |
PURPOSE:To prevent the effect of deviation of the reference voltage on the attenuation in an electronic volume control, and improve the precision of the electronic volume control. CONSTITUTION:An output voltage V0 is generated on the basis of a reference voltage Vref of an electronic volume control 1, a resistance value R4 of a gain setting resistor 23 and a resistance value R5 of a gain setting resistor 24 by means of an inversion amplifier 21. An output voltage V0 is divided into 256 parts in a D/A converter 22, and when the PWM output is supplied from a microcomputer 3 through the external operation, one of the 256 divided parts is outputted as a control voltage Vc from the D/A converter 22 to a control side circuit 8 in the electronic volume control 1. |
