Dual-mode gain control for a 1 V CMOS hearing aid device with enhanced accuracy and energy-efficiency

Abstract

A dual-mode gain control (DMGC) technique is presented for accurate and energy-efficient pre-amplification in the front-end system of a hearing aid chip. Compared with the conventional automatic gain control (AGC) approach, the DMGC approach is characterized by an amplification switching mechanism between the prolinearity discrete gain setting mode and the energy-efficient AGC mode. Thus, the total harmonic distortion (THD) should be significantly improved without incurring any degradation concerning other performances parameters (e.g. gain, noise and power consumption). In order to further enhance the system power efficiency, a self currentadapting (SCA) circuit design technique is proposed. Such SCA circuits are capable of automatically adjusting the bias current in accordance with the sound level. A prototype chip was designed with a 0.13 lm standard CMOS process and tested with 1 V supply voltage. The measurement results show that, for a typical output level of 500 mV p-p , the THD is somewhere below -64 dB, achieving approximately ten times reduction compared to the previously reported works. The power consumption of less than 45 lW has also been obtained. In addition, the typical input referred noise is only 2 lV rms and the maximum gain attainable is up to 39 dB.

An accuracy improved hearing aid readout circuit using a gain-enhanced and OTA-free pseudo-PLL feedback technique

“…The first term represents the ideal output signal, while the second term illustrates the third order harmonic distortion. And the characteristics of a 1 and a 2 [13] could be approximately expressed as follows:…”

High-Precision CMOS Analog Computational Circuits Based on a New Linearly Tunable OTA

“…These circuits realize several functions such as multiplication, division, squaring, square rooting and etc. which are widely used in disk drives [1], hearing aids [2], medical equipment [3], modulators [4], artificial neural networks [5] and fuzzy control systems [6]. There are a lot of techniques to implement analog functional circuits [7][8][9][10][11][12][13][14][15][16][17][18] which can be roughly categorized in three main groups.…”