| 摘要 |
PURPOSE:To obtain the electronic variable resistor which improves sound quality even when a signal has a very low level and can be formed on one chip. CONSTITUTION:With the output of a DELTASIGMA modulator 2, switches SW2-l, SW2-2, SW2-3... and switches SW3-1, SW3-2, SW3-3... are turned ON and OFF first. According to a desired output level, a control signal CONT2 turns ON switches SW1-1, SW1-2, SW1-3... and switches SW4-1, SW4-2, SW4-3.... Namely, respective constant-current sources SKI, SK2, SK3... and constant-current sources S1, S2, S3... are selected (switched ON). Consequently, a current value corresponding to the output of the DELTASIGMA modulator 2 is controlled by the control signal C0NT2 and outputted. The output level is variable by properly varying the control signal C0NT2. |
