Linear attenuator for current-mode digital-to-analog converter (DAC) or the like
US5442352A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 14, 1994 |
| Grant date | Aug 15, 1995 |
| Priority date | — |
| Expiry date | Jan 14, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M1/74
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A linear attenuator (23) for applications such as front/rear audio fading receives an input current to be programmably attenuated according to an input code at an input node (29). A transistor (30) is connected between the input node (29) and inputs of current-steering cells (40, 50, 60), which pass portions of the input current to either an output node (32) or a second node in response to the input code. An amplifier (22) has a negative input terminal connected to the input node (29), a positive input terminal receiving a reference voltage, and an output terminal connected to a control electrode of the transistor (30). The operational amplifier (22) and the transistor (30) together regulate the voltage at the input node (29) to prevent distortion of the input current by making the input node (29) a virtual ground node. Thus the attenuator (23) avoids nonlinearities normally associated with transistors and the need to duplicate a digital-to-analog converter (DAC) (21) providing the input current.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.