| 摘要 |
PURPOSE:To reduce the total higher harmonic distortion ratio in the whole level range from low level to high level by providing a mantissa conversion part, and making the number of converted bits larger when the level of an analog output signal is high or smaller when low. CONSTITUTION:For example, when input data I0-I15 are high in level, namely, when the analog output level Vout is <=-24dB, one of signals S0-S4 is outputted. When the signals S0-S4 are outputted, exclusive OR gates XORs 1 and 2 operate as buffers, signals W and X become equal to a signal M1, and signals Y and X become equal to a signal M0. Therefore, a mantissa part DAC7 operates as a 12-bit DAC in this case. Thus, when the input data are high in level, the mantissa part DAC7 operates as the 12-bit DAC and bit pitch is therefore reduced to suppress higher harmonic distortion. |
