A Low-Voltage Fully Differential Pure Current Mode Current Operational Amplifier

Abstract

In this paper a novel high-frequency fully differential pure current mode current operational amplifier (COA) is proposed that is, to the authors’ knowledge, the first pure MOSFET Current Mode Logic (MCML) COA in the world, so far. Doing fully current mode signal processing and avoiding high impedance nodes in the signal path grant the proposed COA such outstanding properties as high current gain, broad bandwidth, and low voltage and low-power consumption. The principle operation of the block is discussed and its outstanding properties are verified by HSPICE simulations using TSMC $0.18\,\upmu \hbox {m}$ CMOS technology parameters. Pre-layout and Post-layout both plus Monte Carlo simulations are performed under supply voltages of $\pm 0.75\,\hbox {V}$ to investigate its robust performance at the presence of fabrication non-idealities. The pre-layout plus Monte Carlo results are as; 93 dB current gain, $8.2\,\hbox {MHz}\,\, f_{-3\,\text {dB}}, 89^{\circ }$ phase margin, 137 dB CMRR, 13 $\Omega$ input impedance, $89\,\hbox {M}\Omega$ output impedance and 1.37 mW consumed power. Also post-layout plus Monte Carlo simulation results (that are generally believed to be as reliable and practical as are measuring ones) are extracted that favorably show(in abovementioned order of pre-layout) 88 dB current gain, $6.9\,\hbox {MHz} f_{-3\text {db}} , 131^{\circ }$ phase margin and 96 dB CMRR, $22\,\Omega$ input impedance, $33\,\hbox {M}\Omega$ output impedance and only 1.43 mW consumed power. These results altogether prove both excellent quality and well resistance of the proposed COA against technology and fabrication non-idealities.