An important target of the actual research in analog integrated circuit is the design and development of architectures able to operate with low supply voltages. Moreover, low voltage operational amplifiers are building blocks to be used in circuits where a single cell battery supplies the whole system (e.g. "in vivo" biochemical and biomedical sensors, hearing instruments, etc.). A bipolar rail-to-rail low-voltage operational amplifier (op-amp) has been here considered for sensor applications. The input stage is characterized by a full dynamic range and it has a virtually constant transconductance (the maximum DELTAgm is of about 8.5percent), which ensures a constant bandwidth over the whole input common mode voltage. The output stage has been also designed with full swing characteristic. The design offers good performance in terms of simplified architecture, high DC gain, low power consumption, high CMRR, low nose and low input voltage offset. The minimum working supply voltage is 0.85 V. The operative temperature range is (0, 80deg C). The circuit has been designed in a HF2CMOS 2mu BiCMOS technology, provided by SGS-Thomson. An example of differential amplifier topology op-amp to be used in a traditional Wheatstone bridge application is also presented.
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