Design Of GaAs High Speed ASIC

With the quickly development of the electronics and the communication, the demand of higher communication capability and transmission speed requires the semiconductor circuits that can operate at higher frequency. A new semiconductor material whose name is GaAs was found. The electronics mobility in GaAs is six times the mobility of electronics in Si. So the circuits made by GaAs have better performance than the circuits made by Si.The RF switch is a key unit in the RF system. Its performance affect the performance of the RF system. In fact, in order to get a higher speed, lower insertion loss, higher isolation and better power capability, many methods have been put into practice such as the combination of series and parallel connection, new device technology of LDD, the feedback technology, decreasing the control voltages of the system or changing to positive control voltage from the negative one to get the goals. After the compare and analysis, it give us a picture of how to design a RF switch which have high isolation and low insertion loss performance.Base on the study of III-V compound GaAs, I participated in the design of frequency divider using in the communication system. This circuit consists of BFL logic gates, After analyzing the different of up-FET switch and down-FET switch, the performance of down-FET is better than the performance of up-FET. So when we design the circuit of multi-input based on BFL logic, it is better to make the gate voltage of up-FET change before the changing of down-FET gate voltage, in order to make full use of the trans-conductance of MESFET.