| With the increasing demand for high integrated,microminiature portable electronics devices on the market,it makes the needs for low power supply circuits and systems are growing dramatically as well.It is the same as the application and demand for power operational amplifier.However,the continuous shrinking feature size of process brings the lower power supply and smaller device size,which poses a great challenge to the design of analog integrated circuits,especially power operational amplifiers.As an essential part of smart-terminal products,especially,in driving system circuits,power amplifier has the high voltage or high current output characteristic.Its design concepts opposite the developing trend of low voltage,low power,and small size integrated circuit.Therefore,how to design a stable and reliable high current output power operational amplifier under an advanced technology is a topic which is worth studying.The principal objective of this thesis is to implement low voltage,low frequency,high current output operational amplifier in the standard CMOS/CDMOS technology.Given the characteristics of the high current power operational amplifier,this thesis carefully studies and designs the whole system circuit that include the reference circuit,current limit protection circuit,over-temperature protection circuit,shutdown function circuit,etc.and realizes a power operational amplifier chip with a maximum AC current of 390 mA under a 0.5μm 5V CDMOS technology.The main innovations of this paper are the design of reference current source circuit,current limiting protection circuit,shutdown function circuit and the layout design of output stage.This chip not only can realize amplify the analogy input signal,but also can implement shutdown and start-up function through external high/low logic level control signal.In view of the line current driving capability,this design can be applied in systems such as smart phone,cameras,astronomical telescopes,etc.and used to drive the voice coil inductance to realize the system focusing function.This thesis designs a high current power operational amplifier under a standard 0.5μm CMOS/CDMOS technology of MXIC.The power operational amplifier can implement rail-to-rail output,390 mA maximum output current,about 800 mA current limit capability,and can work stably in the industrial standard temperature range(-40℃~125℃).Its extension chip design can also meet the military standard of working temperature range(-55℃~150℃).The design of the external shutdown function control terminal make the operational amplifier can cater for different application scenarios' needs,such as ADC/DAC system,to realize the sequential logic control.Compared with other commercial products with equivalent current output,this design has cost advantages.Because,most high current power amplifier(≥350mA)on the market trend to fabricated under BJT,BCD,FET or other technology,their design are relatively complex and have higher additional cost.Compared with other commercial products with equivalent current output,this design has cost advantages and higher ESD protection capability.The chip has been tested and verified two times.According to the final packaging test and verification,the experimental results are basically consistent with the theoretical design and simulation results of the operational amplifier.It is expected to achieve massive production in the near future. |
