Inductance multiplier circuit
US4767980A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 22, 1987 |
| Grant date | Aug 30, 1988 |
| Priority date | — |
| Expiry date | Oct 22, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/005
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A circuit for increasing the apparent inductance presented by a transformer to a differential signal. The circuit may be used in a battery feed interface circuit for providing battery power to a subscriber's telephone or in a current sink interface circuit for providing a low impedance DC loop closure toward a telephone line feed circuit while maintaining a high impedance for differential AC signals. In either usage the inductance multiplier circuit always multiplies the primary inductance of the transformer by a factor which is one plus a positive number. The transformer has three windings. The multiplication is accomplished by a current source which provides to the third winding a current which flows therein in a manner so as to oppose the current flowing in that winding due to the voltage induced in that winding when the first and second windings are excited by the differential AC signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.