Stepped gain controlled RF driver amplifier in CMOS
US6400227B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | May 31, 2001 |
| Grant date | Jun 4, 2002 |
| Priority date | — |
| Expiry date | May 31, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2200/306
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A variable gain amplifier has at least two branches connected in parallel to drive a common output load. Each branch includes at least two FETs in a cascode configuration. A first FET in each branch is arranged to receive an input signal and to amplify the signal in a common source configuration; the second FET is arranged in a common gate configuration with its source receiving the output current of the first FET. The gate of the second FET is coupled to a corresponding gain control input so that the second FET is enabled when the gate receives an enabling gain control signal and disabled otherwise. Preferably the first and second FETs in each branch are biased in a saturation region of operation when the second FET is enabled by the gain control input. This maintains a low distortion figure throughout the dynamic range of the gain control. Preferably, the invention also includes an active fixed gain power amplification stage for coupling the output to a power amplifier.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.