Design and analysis of the quadfferential amplifier

  • Authors:

  • Tina Marie Rookmaaker;Moon Seok Kim;Yong-Bin Kim

  • Affiliations:

  • Analog Devices, 804 Woburn Street, Wilmington, MA 01887, USA;263 Egan Research Center, Northeastern University, 360 Huntington Ave, Boston, MA 02115, USA;327 Dana Research Center, Northeastern University, 360 Huntington Ave, Boston, MA 02115, USA

  • Venue:
  • Microelectronics Journal
  • Year:
  • 2012

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Abstract

This paper presents a design and analysis of a quadfferential amplifier for a CAT5 cable. A quadfferential amplifier consists of four inputs, four outputs, and a V"o"c"m pin which controls the output common-mode voltage (Erdi, 1970 [1]). It is similar to the differential amplifier in that it amplifies differences and rejects overall input common-mode. The transfer function shows that quadfferential amplifier requires symmetry of feedback and gain resistors to approach its ideal behavior. Using a graphical approach the amplifier is compensated to drive a capacitive load of 50pF. The output current drive is designed for minimum load resistance of 150@W. Performing Monte Carlo simulations to evaluate offset voltage and common-mode rejection shows the mean offset voltage of 265@mV and a common-mode rejection of 126dB.