Design of a low-current shunt-feedback transimpedance amplifier with inherent loop-stability

Abstract

In this paper we propose a new architecture for enhancing the performance of a transimpedance amplifier (TIA) used for low-currents, and in particular, that used in biosensing. It is usually the first block in biomedical acquisition systems for converting a current in the nanoampere and picoampere range into a proportional voltage, with an amplitude suitable for further processing. There exist two main amplifier topologies for achieving this, current-mode and shunt-feedback mode. This paper introduces a shuntfeedback amplifier that embodies current-mode operation and thereby offers the advantages of both existing schemes. A conventional shunt-feedback amplifier has a number of stages and requires compensation components to achieve stability of the feedback loop. The exemplary circuit described is inherently stable because a high gain is effectively achieved in one stage that has a dominant pole controlling the frequency response. Exhibiting complementary symmetry, the configuration has an input port that is very close to earth potential. This enables the configuration to handle bidirectional input signals such are as met with in electrochemical ampero-metric biosensors. For the 0.35µm process adopted and ±3.3V rail supplies, the power dissipation is 330µW. With a transimpedance gain of 120dBohm the incremental input and output resistances are less than 2ohm and the-3dB bandwidth for non-optical input currents is 8.2MHz. The input referred noise current is 3.5pA/√Hz.

A 1.8 V Low-Power Low-Noise High Tunable Gain TIA for CMOS Integrated Optoelectronic Biomedical Applications

“…Finally, Table 2 summarize the main characteristics, performances and parameters of the proposed circuit together with those ones of similar solutions reported in the literature. In particular, by comparing present results with those ones from comparable solutions specifically designed for biomedical applications [24,26], the proposed TIA Besides, from the bias point analysis, the resulting stand-by power consumption of the circuit is about 33 µW with a DC input current I IN = 1 nA (i.e., the PD dark photocurrent). In order to evaluate the circuit power consumption under the AC pulsed regime, the PD pulsed photocurrent I IN previously described has been also considered and under these operating conditions the circuit power consumption varies from 33.1 up to 36.1 µW for the transimpedance gain equal to 102 dB and 124 dBΩ, respectively.…”

“…From the above-mentioned applications, it is evident that the electronic front-end of the sensors must be designed to comply with demanding characteristics for what concerns the minimum detectable current/voltage signal that is directly related, for example, to the determination of the lowest concentration of chemical/biochemical substances to be detected and/or to the smallest displacement to be actuated in wearable prosthetics. Independently from the specific application, the front-end of sensor devices is generally based on specific transimpedance amplifiers (TIA) as the first conditioning circuits that, for all the applications outlined before, need to operate under low-voltage and low-power conditions [17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

A 180 nm CMOS Integrated Optoelectronic Sensing System for Biomedical Applications

“…In general, optical sensors are devices composed of a semiconductor laser or which are LED emitting at the wavelength required from the specific application and of the Si photodiode (PD) that generates a photocurrent proportional to the light intensity illuminating its sensitive area. The electronic analog front-end of optical sensors is typically based on transimpedance amplifiers (TIA) that convert the input photocurrent to an amplified voltage signal operating, as much as possible, under low-voltage and low-power conditions [9,[18][19][20][21]. Moreover, in several applications, the TIA should provide a high gain and be supported by a real-time automatic gain control/compensation sub-system.…”

Low input-resistance low-power transimpedance amplifier design for biomedical applications

“…For accuracy, the incremental input resistance of the TIA is required to be low, i.e., in the ohmic region. A number of methods exists to achieve this [13][14] [15]. One particular method that has been favoured because it offers a range of attractive features has been called a 'super-common-gate amplifier' [16] and it forms the starting point for the problem in hand for the new circuit presented in this paper.…”