Design of Lowpass Leapfrog Ladder Filter and Quadrature Oscillator Using Active Current-Mode Elements

• Main Authors: Kuo-Fu Lee, 李國甫
• Other Authors: Jiun-Wei Horng
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/16477271196550244577

碩士 === 中原大學 === 電子工程研究所 === 93 === A new lowpass filter using current-feedback amplifiers with the leapfrog design method is presented. The passive LC ladder filter is used to construct the leapfrog filter. The new approach offers simple realization process and low sensitivity. A new voltage-mode quadrature oscillator using one unity-gain current follower (CF), three unity-gain voltage followers (VFs), three resistors and three grounded capacitors is presented. Outputs of two voltage-mode sinusoidal signals with 90o phase difference are available in the proposed quadrature oscillator. The oscillation condition and oscillation frequency are orthogonally controllable through different passive components. The tracking errors of the unity-gain cells have no effects on the oscillation frequency. The proposed circuit employs only grounded capacitors. The use of only grounded capacitors is ideal for integrated circuit implementation. By adding one more unity-gain current follower to the proposed circuit, the current-mode quadrature output signals can also be obtained. Besides, The influence of parasitic elements and jitter are analyzed and discussed in the thesis.