新型寬動態範圍可程式化增益控制器的設計分析與實現

Abstract

本論文探討了寬動態範圍可程式化增益控制器的架構與設計，可運用在多 媒體音效卡上多音源輸入的混波器晶片中。在傳統的增益控制電路設計上 是以運算放大器、電阻及類比開關等元件所構成，在晶片的實現過程中會 發生晶片面積過大的缺點，而精確的電阻值需藉由雷射來予以修正，因而 增加了開發的成本。本論文中設計了一個具有數位化界面的可程式型衰減 器，其衰減範圍為 0 dB 到 -79 dB，具有 80 階的衰減選擇，每階為 -1 dB，並具有靜音功能。在此次的電路實作，我們並未對電路上的非理 想效應加以考慮與消除，由模擬的結果得到：在衰減範圍 0 dB 到 -59 dB時的誤差範圍在-0.53 dB 到 0.11 dB 之間、而在衰減範圍 0 dB 到 -79 dB 時的誤差範圍在-0.83 dB 到 -0.19 dB。此電路再經消除非理想 效應後，可應用於音效卡的晶片組中，亦可應用於各種音量控制電路上， 達到數位化音量控制的目的。 This thesis deals with the design and implementation of a new wide-dynamic-range programmable gain controller, integrated with the mixer chip for the audio card of multimedia system. In the conventional design, the circuit consists of OP-Amps, resisters, capacitors, and analog switches. The main disadvantage of the design is that more chip area is needed due to a large amount of resistors and capacitors. Moreover, the accurate resistance value is obtained by laser-trimming which it increases the cost. In this thesis, a new structure is proposed to implement the programmable gain controller with a wide dynamic range. The proposed programmable gain controller( PGC) circuit has the 80 level settings of the LOSS range from 0 dB to -79 dB by a step of -1 dB. It has the monotonically logarithmic increments with maximum deviation of -0.53 dB in the range of 0 dB to -59 dB and -0.83 dB in the range of 0 dB to-79 dB. It fits the specification for the audio card of the multimedia systems. This circuit can also be applied to the volume control circuit as the programmable volume controller.