A Broadband Amplifier With Flat Bandwidth for Modulator and Measurement Driver Circuits

This paper presents a broadband amplifier for high-speed modulators and measurement driver circuits using distributed amplifiers configuration. The flat low-frequency performance of the conventional distributed amplifiers (DAs) is limited by termination impedance. This paper shows on-chip low frequency extension can be achieved by optimizing the capacitively coupled circuit and impedance termination. Although capacitively coupled circuit has been introduced in previous studies to extend the high-frequency gain, sufficient analysis has not been studied. Furthermore, a novel broadband equalizer termination applying for distributed configuration is introduced that can be employed to balance the rising gain. This DA features the lowest cut-off frequency among broadband amplifiers using the on-chip circuit. The amplifier provides a comparable low-frequency performance of MHz with greater than 15 dB gain and benchmarks the first demonstration of a flat MHz performance monolithic microwave integrated circuit (MMIC) using on-chip passive components. The proposed amplifier achieves 17 dBm output 1dB compression point (OP1dB) covering eight-octave bandwidth verified using a 0.15-μm GaAs pseudomorphic High Electron Mobility Transistor (pHEMT) technology. The new design architecture combined with the broadband equalizer characteristics and gate series network can provide performance benefits for optic modulators, instrumentations, and advanced broadband transmitters.