Bipolar monolithic amplifiers for a gigabit optical repeater

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 μm 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.