Area-efficient current-input filter, virtual ground circuit used in same, and method therefor
US5412335A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 14, 1994 |
| Grant date | May 2, 1995 |
| Priority date | — |
| Expiry date | Jan 14, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H11/04
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A filter (62) receives an input current signal and provides a filtered output signal in response. The filter (62) presents an extremely low-impedance input node (72) to the source of the input current signal, such as a current digital-to-analog converter (DAC) (62), thus avoiding modulating the input current signal. The filter (62) includes a virtual ground circuit (70) connected to the input node (72) followed by a filter (80) such as a biquad filter. The virtual ground circuit (70) has a high-gain cascoded loop to provide an intermediate current at a high-impedance output terminal (82), which is connected to an input terminal of the filter (80). The virtual ground circuit (70) is implemented without operational amplifiers and resistors, thus providing high linearity without a large amount of integrated circuit area.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.