A Wideband Inductorless dB-Linear Automatic Gain Control Amplifier Using a Single-Branch Negative Exponential Generator for Wireline Applications

This paper reports a wideband inductorless automatic gain control (AGC) amplifier for wireline applications. To realize a dB-linear AGC range, a pseudo-folded Gilbert cell driven by a single-branch negative exponential generator (NEG) is proposed as the core variable-gain amplifier. The NEG features a composite of dual Taylor series to extend the AGC approximation range without sacrificing the precision. Fabricated in 65-nm CMOS, the AGC amplifier occupies a tiny die area of 0.045 mm
²
and consumes 28 mW at 1.2 V. Measured over a dB-linear gain range of ~40 dB, <; ± 1 dB gain error is achieved and the 3-dB bandwidth stays roughly constant at 7 GHz. For the closed-loop AGC measurement, the input dynamic range is ~40 dB (10 mVpp to 1 Vpp) for a BER <;10
^-12
under a 2
⁷
- 1 PRBS data at 10 Gb/s. The achieved figure-of-merit (FOM) of 2.8 pJ/bit compares favorably with state-of-the-art.