On-chip GaAs-HBT broadband-coupled high-bitrate modulator driver TWAs

A technique to connect two broadband GaAs HBT TWAs is presented. It covers the full range from DC to high frequency and is suitable for high bitrate (40 Gb/s) transmission circuits. This behavior is achieved by modifying the response of one TWA so that it compensates the low-frequency losses. This technique is truly broadband because it uses only elements which are directly connected, and thus is not limited at very low frequencies. Each single TWA delivers 8 dB of broadband gain at a 3 dB cut-off-frequency of 26 GHz. Using this interconnect technique, a total broadband gain of 14.5 dB is obtained.