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چکیده
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Sound Navigation and Ranging (SONAR) are widely deployed in marine applications, locating submarines, underwater research, weather forecasting, oil and gas exploration, and medical fields. There are three types of SONAR: passive, active, and recently hybrid SONARs. Passive SONAR deals with weak signals at low frequencies (<10kHz), demanding low offset and low flicker noise amplifiers, while active SONAR works at higher frequencies (up to MHz), calling for low thermal noise and wide UGBW amplifiers. Hybrid SONAR covers both low and high-frequency bandwidth, and its amplifier requires all mentioned features. Although the chopping technique is a remedy to reduce the flicker noise in multi-stage amplifiers, the input bias current and the residue offset are proportional to the chopping frequency, fch. Furthermore, increasing fch demands for increasing UGBW and power consumption of the amplifier rarely exceed a few hundred kHz and limits its high-frequency applications. This paper proposes an OpAmp with 69MHz UGBW, 40V/μs SR at 100pF load cap, 3nV/√Hz input referred thermal noise PSD, lower than 4.5μV offset voltage, and only 1.5nA input current at 2.5MHz fch, while the circuit draws 3.3mA from 1.8V. This is made possible by introducing a new compensation scheme, modified biasing circuitry for the rail-rail input gm stage, and presenting low input current bootstrap switches.
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