3 May 2011 A 55 μW programmable gain amplifier with constant bandwidth for a direct conversion receiver
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Abstract
A fully differential programmable gain amplifier (PGA) with constant transfer characteristic and very low power consumption is proposed and implemented in a 130 nm CMOS technology. The PGA features a gain range of 4 dB to 55 dB with a step size of 6 dB and a constant bandwidth of 10-550 kHz. It employs two stages of variable amplification with an intermediate 2nd order low-pass channel filter. The first stage is a capacitive feedback OTA using current-reuse achieving a low input noise density of 16.7 nV/√Hz. This stage sets the overall high-pass cutoff frequency to approximately 10 kHz. For all gain settings the high-pass cutoff frequency variation is within ±5%. The low-pass channel filter is merged with a second amplifying stage forming a Sallen-Key structure. In order to maintain a constant transfer characteristic versus gain, the Sallen-Key feedback is taken from different taps of the load resistance. Using this new approach, the low-pass cutoff frequency stays between 440 kHz and 590 kHz for all gain settings (±14%). Finally, an offset cancelation loop reduces the output offset of the PGA to less than 5 mV (3σ). The PGA occupies an area of approximately 0.06 mm2 and achieves a post-layout power consumption of 55 μW from a 1V-supply. For the maximum gain setting the integrated input referred noise is 14.4 μVRMS while the total harmonic distortion is 0.7 % for a differential output amplitude of 0.5 V.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jens Masuch, Jens Masuch, Manuel Delgado-Restituto, Manuel Delgado-Restituto, } "A 55 μW programmable gain amplifier with constant bandwidth for a direct conversion receiver", Proc. SPIE 8067, VLSI Circuits and Systems V, 80670B (3 May 2011); doi: 10.1117/12.886994; https://doi.org/10.1117/12.886994
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