CMOS Analog AGC for Biomedical Applications

Abstract

In this paper, we present the design of an analog Automatic Gain Control with a small silicon area and reduced power consumption using a 0.5 μ m process. The design uses a classical approach implementing the AGC system with simple blocks, such as: peak detector, difference amplifier, four-quadrant multiplier, and inversor amplifier. Those blocks were realized by using a modified Miller type OPAMP, which allows indirect compensation, while the peak detector uses a MOS diode. The AGC design is simulated using the Tanner-Eda environment and Berkeley models BSIM49 of the On-Semiconductor C5 process, and it was fabricated through the MOSIS prototyping service. The AGC system has an operation frequency of around 1 kHz, covering the range of biomedical applications, power consumption of 200 μ W, and the design occupies a silicon area of approximately 508.8 μ m × 317.7 μ m. According to the characteristics obtained at the experimental level (attack and release time), this AGC can be applied to hearing aid systems.

Design of an automatic gain control loop for high speed communication

“…AGC is a closed loop system that maintains the output level constant while the input level may change considerably 6 . The input–output characteristics of an ideal AGC are shown in Figure 1 7 . For a small input signal, the AGC loop does not operate, and the output signal changes linearly with respect to the input signal.…”

“…6 The input-output characteristics of an ideal AGC are shown in Figure 1. 7 For a small input signal, the AGC loop does not operate, and the output signal changes linearly with respect to the input signal. This is due to the fact that the AGC loop might not have sufficient gain for very low input signals.…”