Precise, portable and wide band alternating current source for extremely low current values

Abstract

Alternating current (AC) sources which provide currents in micro ampere ranges have become essential for testing of electronic components, simulation of sensors, eddy current analysis, small signal analysis of transistors, electro-cutaneous stimulation in therapeutics, current injection in medical imaging techniques etc. This manuscript proposes a precise voltage mode AC source for extremely low current values. A simple AC source with load in the feedback is optimised experimentally by compensating the capacitive effects (approx. 4.7 pF) by employing a novel combination of general impedance converter (gic) or Negative Capacitance Converter (NCC) circuits along with basic circuit. The design is proposed with precise value of 160 μ A for applications including physiological measurements. It is seen that GIC circuit modification offers better consistency and performance in load analysis compared to NCC. Load analysis (10–2000 Ω), frequency analysis (100 Hz to 1 MHz), stability analysis and reliability testing confirm the optimised and precise operation of the proposed current source. With very high degree of matching in theoretical and practical results, calculation of output impedance is also done and the value is fair enough. The hardware incorporates direct digital synthesis chip driven by a microcontroller for generation of sine wave, thereby reducing the need of bulky power supplies and function generators. This precise alternating current source is suitable for wide band portable applications.