AGC loop implementation using temperature compensated CMOS linear-in-dB VGA

In this paper, an Automatic Gain Control (AGC) loop is proposed which is based on a linear-in-dB Variable Gain Amplifier (VGA). The VGA structure is based on simple nMOS differential pairs. The linear-in-dB gain tuning schema is designed using a novel exponential generator which it offers also temperature compensation of the VGA's gain. The proposed implementation is designed in 90nm CMOS process with 1.2V supply voltage. The gain of the VGA is tuned by a control voltage with gain range equal to 27dB with ±1dB linearity error. The worst case variations of the VGA gain, over process and temperature corners, are ±1.54dB and ±2.45dB for maximum and minimum gain setting, respectively.

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