Low-pass filter and voltage-current conversion circuit used in the same
US7466192B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 25, 2007 |
| Grant date | Dec 16, 2008 |
| Priority date | — |
| Expiry date | May 9, 2027 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2203/45528
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A low-pass filter with a high signal-to-noise ratio is provided. A low-pass filter includes a first RC filter circuit, a differential operation circuit subtracting an output signal from a low frequency component of an input signal and outputting a differential signal, a second RC filter circuit, a voltage-current conversion circuit, and a capacitor. The voltage-current conversion circuit includes an operational amplifier, a first resistor, and a feedback circuit generating a feedback voltage in accordance with a voltage applied to the first resistor. If resistance values of first to fourth resistors are R1, R2, R3, R4, a relational expression of R1*R3=R2*R4 is satisfied, and output current i becomes constant regardless of a resistance value of a load resistance. Since only a first resistor is connected between the input and the output of the voltage-current conversion circuit, thermal noise decreases, and a signal-to-noise ratio becomes high.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.