Bipolar monolithic amplifiers for a gigabit optical repeater

Abstract

Main amplifier, AGC amplifier, and preamplifier ICs have been designed and fabricated using an advanced silicon bipolar process to provide the required characteristics of repeater circuits for a gigabit optical fiber transmission system. The bipolar technology used involved a separation width of 0.3 /spl mu/m between the emitter and the base electrode. New circuit techniques were also used. The differential type main amplifier has a peaking function which can be varied widely by means of DC voltage supplied at the outside IC terminal. A bandwidth which can be varied to about three times the value for a nonpeaking amplifier is easily obtained. The gain and maximum 3-dB down bandwidth were 4 dB and 4 GHz, respectively. The main feature of the AGC amplifier is that the diodes are connected to the emitters of the differential transistor pair to improve the linearity. The maximum gain and 3-dB down bandwidth were 15 dB and 1.4 GHz, respectively, and a dynamic range of 25 dB was obtained. The preamplifier has a shunt-series feedback configuration. Furthermore, a gain and 3-dB down bandwidth of 22 dB and 2 GHz, respectively, were achieved with an optimum circuit design. The noise figure obtained was 3.5 dB.