A 1 GHz equiripple low-pass filter with a high-speed automatic tuning scheme

Tien Yu Lo*, Chung-Chih Hung

*Corresponding author for this work

Research output: Contribution to journalArticle

19 Scopus citations


A continuous-time fourth-order equiripple linear phase G m-C filter with an automatic tuning circuit is presented. A high speed OTA based on the inverter structure is realized. The combined common-mode feedforward and common-mode feedback circuit ensures the input and output common-mode stability. The gain performance could be maintained by combining an equivalent negative resistor circuit at the output nodes. Transconductance tuning can be achieved by adjusting the bulk voltage by using the deep-NWELL technology. The modified automatic tuning circuit relaxes the speed requirement of the tuning blocks. Through the use of the operational transconductance amplifier as a building block with the automatic tuning scheme, the filter -3 dB cutoff frequency is 1 GHz with the group delay less than 4% variation up to 1.5 fc frequency. The -43 dB of IM3 at filter cutoff frequency is obtained with -4 dbm two-tone signals. Implemented in 0.18-μm CMOS process, the chip occupies 1 mm 2 and consumes 175 mW at a 1.5-V supply voltage.

Original languageEnglish
Article number5325666
Pages (from-to)175-181
Number of pages7
JournalIEEE Transactions on Very Large Scale Integration (VLSI) Systems
Issue number2
StatePublished - 1 Feb 2011


  • Automatic tuning circuit
  • deep N-WELL technology
  • equiripple linear-phase
  • operational transconductance amplifier (OTA)

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