Variable time constant circuit and filter circuit using the same
US6977541B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 24, 2003 |
| Grant date | Dec 20, 2005 |
| Priority date | — |
| Expiry date | Dec 24, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2203/45652
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A variable time constant circuit includes an inverting amplifier which has an amplifier input terminal and an amplifier output terminal connected to a signal output terminal and inverts a signal inputted to the amplifier input terminal, a first and a second resistor which are connected in series between the signal input terminal and the amplifier input terminal, a capacitor connected between the amplifier input terminal and the amplifier output terminal, a field effect transistor including a gate terminal connected to a junction point of the first and second resistors, a source terminal kept at a constant potential, and a drain terminal connected to the amplifier input terminal, the transistor flowing a current through the drain terminal according to a voltage between the gate terminal and the source terminal, and a control circuit which controls a voltage-current conversion ratio of the transistor according to a time constant control signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.