Sierra Semiconductor

Joseph N Babanezhad

Roubik Gregorian

The output stage of a differential operational amplifier includes a source follower amplifier and a common source amplifier which are driven by two complementary outputs of a differential input stage. Continuous-time feedback circuits are provided to set the quiescent biasing conditions accurately. The differential operational amplifier has a low output impedance and a large output voltage swing with negligible open loop gain degradation when the size of the load resistance is varied. Floating compensation capacitors reduce the total capacitor value and the physical area needed for the operational amplifier.

Differential operational amplifier

A CMOS operational amplifier comprises an output gain stage including output transistors coupled between the rails so that for a given amount of current, the output transistors have rail-to-rail gate-to-source voltages. The output transistors can be made smaller in size with the output stage being capable of driving a small resistive load with minimal signal distortion.

Rail-to-rail CMOS operational amplifier

An exponential analog-to-digital converter comprises two gain stages, each of which includes a binary-weighted capacitor array. The capacitors are switched in succession to multiply the gain of a sampled analog input signal, while a counter counts down for each switching step from an initial setting of binary 111. When the gain signal has a value outside a predetermined reference voltage range, a 3-bit binary digital word representative of the analog input signal sample is registered in the counter. If the gain signal produced after all the capacitors have been switched in to provide the maximum gain does not fall outside the reference range, then the binary word stored in the counter for the sample of the analog signal is 000.

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Campbell, CA, United States of America

Joseph N Babanezhad