A circuit including an oscillator circuit, a current generator circuit and a voltage generator circuit. The oscillator circuit may be configured to generate an output signal having a frequency in response to (i) a first control signal and (ii) a second control signal. The current generator may be configured...http://www.google.com.hk/patents/US6191660?utm_source=gb-gplus-share專利 US6191660 - Programmable oscillator scheme
