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.
Highlights
Chronic diseases are considered the main cause of death in the world, with cardiovascular, oncological and respiratory diseases, as well as cerebrovascular accidents and diabetes comprising54% of deaths in 2016 [1]
The Automatic Gain Control (AGC) design is based on an modified Miller type operational amplifier (OPAMP) with indirect compensation and a class-A output as shown in Figure 5, which is composed of a differential pair (M3 –M4 ), followed by an output stage comprising a type-A amplifier (M9 –M10 ) and a capacitor (Cc )
The multiplier used for this work is the well-known Gilbert cell [26] shown in Figure 7, which is comprised by 6 transistors operating in the saturation region (M3 –M8 ) and a bias current mirror (M1 –M2 ).The design of this circuit was proposed using equation 1 for a gain-bandwidth product (GBW) = 4 MHz and a capacitance of 10 pF due to the load represented by an internal pad, obtaining a gm1 = 251.32 μs
Summary
Chronic diseases are considered the main cause of death in the world, with cardiovascular, oncological and respiratory diseases, as well as cerebrovascular accidents and diabetes comprising. Electronics 2020, 9, 878 use of an Analog Automatic Gain Control (AGC) to handle amplitude changes in biomedical signals to adequate the signal into the input range of the ADC. Release time (R T ): Time required for the AGC to respond to an abrupt loss in amplitude It is quantified from when the input signal changes up until it amplifies the output signal to a value close to the VREF with a tolerance. The mathematical description of the transfer function is taken from [24]
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