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

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 μm 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 _p-p differential input signal, sampled at a rate of 1 MS/s