Các đầu vào khác biệt giữa các tín hiệu u ~ và UIN được đưa vào một thác ba theo p nguồn, MI, M i, M2, Mi, M?, Và M i, cung cấp chuyển đổi trở kháng và mức độ thay đổi. Theo nguồn được thực hiện với tăng cường chế độ FETs, | RESEARCH DIRECTIONS 307 In GaAs-HFET technology a 20-Gb s laser driver has been reported in 196 40-Gb s modulator drivers with a single-ended swing of Vpp and 6Vpp have been reported in 79 and 172 respectively. In InP-HBT technology a 20-Gb s modulator driver with single-ended swing and a 40-Gb s EAM driver with single-ended swing have been reported in 89 and 66 respectively. Higher Integration. Another area of research aims at higher integration by combining the laser diode monitor photodiode and the driver circuit on the same chip creating a so-called optoelectronic integrated circuit OEIC . For example a complete transmitter consisting of a distributed feedback DFB laser and an HFET driver circuit have been integrated on a single InP substrate 84 . However it is a challenge to combine laser and circuit technologies effectively into a single one because of the significant structural differences between lasers and transistors. For example lasers require mirrors or gratings for their operation whereas transistors don t. As a result transmitter OEICs are not as far advanced as receiver OEICs. An alternative to the above-mentioned monolithic OEICs is the integration of lasers and drivers by means of flip-chip technology. An important advantage of this flip-chip OEIC approach is that the technologies for the laser chip and the driver chip can be chosen and optimized independently thus avoiding the compromises of monolithic OEICs. Lower Power. With increasing miniaturization of the transceiver modules the heat generated by the driver becomes a more serious problem. When using an uncooled laser the heat from the driver may degrade the laser s performance and lifetime when using a cooled laser the thermoelectric cooler must work extra hard to remove the heat from the laser and the driver. Therefore low-power laser drivers are a subject of great interest. The power dissipation and the associated heating can be reduced by lowering the supply voltage and
