A Monolithic amplifier IC with small phase deviation applying parallel feed back technique was developed by using high speed Si bipolar process technology. This IC achieves a phase deviation of 1.8, an S21 gain of 46 dB and a limiting output of 7.8 dBm at 1 GHz.

A high-gain wide-band amplifier IC module is needed for high-speed communication systems. However, it is difficult to expand bandwidth and maintain stability. This is because small parasitic influences, such as bonding-wire inductance or the capacitance of the package, become large at high frequencies, thus degrading performance or causing parasitic oscillation. In this paper, a new design procedure is proposed for the high-gain and wide-band IC module, using stability analysis and a unified design methodology for IC's and packages. A multichip structure is developed using stability analysis and the requirements for stable operation are determined for each IC chip, package, and interface condition between them. Furthermore, to reduce the parasitic influences, several improvements in the interface and package design are clarified, such as wide-band matching and LC resonance damping. IC design using effective feedback techniques for enlarging the bandwidth are also presented. The IC's are fabricated using 0.2-µm GaAs MESFET IC technology. To verify the validity of these techniques, an equalizer IC module for 10-Gb/s optical communication systems was fabricated achieving a gain of 36 dB and a bandwidth of 9 GHz.

This paper describes a distributed amplifier IC module and a distributed 1 : 2 signal distributor IC module for 40-Gbit/s optical transmission systems. These ICs were designed by the distributed circuit and inverted-microstrip-line design technique and fabricated using 0. 1-µm-gate-length GaAs MESFETs with a multilayer interconnection structure. These were mounted on a thin film multilayer substrate in a chip-size-cavity package by means of a flip-chip-bonding technique that uses transferred microsolder bumps. The amplifier module achieved a 3-dB bandwidth of more than 50 GHz and a gain of 8 dB. The 3-dB bandwidth of a 1 : 2 signal distributor module was 40 GHz and the loss was 2 dB. These modules were demonstrated at 40 Gbit/s and clear eye openings were confirmed.

An extremely accurate and very wide-band quadrature modulator IC fabricated on a single chip using bipolar technology is presented. The characteristics of this quadrature modulator IC are much superior to conventional ones (modulation phase error and deviation from quadrature is about 1/10), and this IC is applicable to high modulation schemes such as 256 QAM. In this circuit, the phase difference between local signals input to each of two balanced modulators is detected by a phase detector, and a variable phase shifter in the local port is controlled automatically by the detected signals. This, along with the use of a wide-band variable phase shifter, enables the phase difference between the local signals input to the balanced modulators to be adaptively controlled to 90 degrees in wide frequency bands. In addition, a design method for the balanced modulators to obtain small modulation phase error is described. Based on this design method, a highly accurate quadrature modulator IC was fabricated, in which two balanced modulators, the phase detector, and the variable phase shifter were integrated on a single chip. Phase deviation from quadrature in the local signals was reduced to less than 0.3 degrees in the wide frequency bands of more tham 60 MHz. The modulation phase error of the balanced modulators wes less than 0.2 degrees at 140 MHz, and less than 2.5 degrees at up to 1.3 GHz.

BP-LDD n+ self-aligned GaAs-MESFETs with Au/WSiN bilayer gate have been fabricated on 3-indiameter GaAs substrate which demonstrates the splendid potentiality of GaAs-MESFET technology. The 0.3-µm gate GaAs-MESFETs show a peak extrinsic transconductance of 550 mS/mm with a threshold voltage of -1.4 V. From S-parameter measurement, the MESFETs demonstrate a peak cutoff frequency of 56 GHz and a maximum oscillation frequency of 120 GHz. Moreover, a monolithic distributed amplifier has been fabricated using the four GaAs-MESFETs with 0.3 µm gate length. The amplifier has achieved a high gain of 7.3 dB with a 3-dB down frequency bandwidth of 0.5-30 GHz.