Low-voltage analog circuit design based on biased inverting opamp configuration

Abstract

Analog circuit designs that use inverting opamp configuration can be converted into low-voltage designs by biasing the opamp input common-mode voltage to near one of the supply rails. This is achieved by introducing a current source or a resistor between the opamp negative input terminal and one of the supply rails. Hence, in this technique, opamps with limited input common-mode range can be used. In addition, switches can be incorporated in these circuits to allow a wide range of applications. This technique also allows large input and output signal swings (close to rail-to-rail), even at a very low-voltage supply. To demonstrate the proposed technique, four track-and-hold amplifiers (THA's) and a 10 bit digital-to-analog converter (DAC) have been designed in a conventional 1.2 /spl mu/m CMOS process and tested at a 1 V supply. The DAC consumes less than 0.45 mW and has a maximum throughput of 1 MS/s, with close to rail-to-rail output (0.1-0.9 V). The maximum differential nonlinearity error and integral nonlinearity error were measured to be 1.7 least significant bits (LSB's) and 3.0 LSB's, respectively. Each THA dissipates less than 0.35 mW and achieves a hold mode total harmonic distortion of less than -61 dB for a 100 kHz, 1.4 V/sub p-p/ differential input signal, sampled at a rate of 1 MS/s.