High-Output Voltage Swing in Silicon Broadband Distributed Amplifiers

The various foundries are now producing CMOS, SiGe and BiCMOS technologies with device speeds that are comparable to some of the III-V technologies. Electro-optical modulators typically are driven with voltages in the range of a few volts to tens of volts, and recent research is producing silicon modulators that require voltages as low as one to two volts. Therefore, a silicon distributed amplifier could be used as a pre-driver, or driver, for the electro-optical modulator if it is able to achieve a minimum one to two volt peak-to-peak swings to drive a silicon electro-optical modulator.The research is an exploration of techniques aimed at improving the large signal output performance of silicon distributed amplifiers for use in fibre optic communication systems. The experimental verification of these techniques involves the design and implementation of several distributed amplifiers in a standard readily available silicon process; ST Microelectronics BiCMOS9 process with eight metal layers and a minimum drawn length of 0.13 microns. A novel distributed amplifier topology has been designed that has artificial transmission lines composed of m-derived filter sections to increase the 3dB passband and a gain stage that increases the bandwidth over that which is available from a single device. The gain stage topology allows the designer to trade the extended bandwidth for the gain necessary to achieve a large output voltage swing. Three distributed amplifiers with bandwidths suitable for 40 gigabit per second data rates have been designed and fabricated and are as follows:•A CMOS single-ended five-stage cascoded fT doubler distributed amplifier producing better than 1V peak-to-peak output voltage swing.•A HBT single-ended three-stage cascoded fT doubler distributed amplifier producing better than 2V peak-to-peak output voltage swing.•A HBT three-stage cascode differential to single-ended distributed amplifier producing better than 2V peak-to-peak output voltage swing.