Compact Current Reference Circuits with Low Temperature Drift and High Compliance Voltage

Abstract

Highly accurate and stable current references are especially required for resistive-sensor conditioning. The solutions typically adopted in using resistors and op-amps/transistors display performance mainly limited by resistors accuracy and active components non-linearities. In this work, excellent characteristics of LT199x selectable gain amplifiers are exploited to precisely divide an input current. Supplied with a 100 µA reference IC, the divider is able to exactly source either a ~1 µA or a ~0.1 µA current. Moreover, the proposed solution allows to generate a different value for the output current by modifying only some connections without requiring the use of additional components. Experimental results show that the compliance voltage of the generator is close to the power supply limits, with an equivalent output resistance of about 100 GΩ, while the thermal coefficient is less than 10 ppm/°C between 10 and 40 °C. Circuit architecture also guarantees physical separation of current carrying electrodes from voltage sensing ones, thus simplifying front-end sensor-interface circuitry. Emulating a resistive-sensor in the 10 kΩ–100 MΩ range, an excellent linearity is found with a relative error within ±0.1% after a preliminary calibration procedure. Further advantage is that compliance voltage can be opposite in sign of that obtained with a passive component; therefore, the system is also suitable for conditioning active sensors.

A current reference with wide temperature operation range and low temperature drift

“…Within a certain load range (≤2 MΩ), the output reference current can remain stable at 1.2 μA. The minimum operation voltage of the circuit is 1.6 V. Although this design has certain advantages compared with others in Table 1, it still has some shortcomings compared with solutions based on commercial product REF200 in [8], such as working voltage range and load resistance range. Therefore, there is still much room for improvement of this design in the future.…”

Stability analysis and design of floating load voltage‐controlled current sources

“…The analysis of the literature and technical documentation showed the existence of two basic types of circuit configurations that work with floating or grounded load. In previous works, [5][6][7][8][9][10][11][12][13][14] different circuits of voltage-to-current converters with grounded load are presented, in which various useful structural modifications and frequency compensations with external passive components are proposed for improving the stability in a given frequency range, as well as increasing the value of the output resistance. Moreover, the majority of the electronic circuits [3][4][5][6][8][9][10][11][12]14 are based on the Improved Howland Current Pump, which uses one op-amp and five (or six) resistors.…”

“…In previous works, [5][6][7][8][9][10][11][12][13][14] different circuits of voltage-to-current converters with grounded load are presented, in which various useful structural modifications and frequency compensations with external passive components are proposed for improving the stability in a given frequency range, as well as increasing the value of the output resistance. Moreover, the majority of the electronic circuits [3][4][5][6][8][9][10][11][12]14 are based on the Improved Howland Current Pump, which uses one op-amp and five (or six) resistors. For the Improved Howland Current Pump, with an accurate selection of the ratios of the resistors and proper selection of the op-amp, the independence of the output current from the voltage drop over the load can be achieved, as well as the bandwidth can up to about 100 kHz 6,10,[12][13][14] and in some cases up to 1 MHz.…”

Electronics for Sensors

“…This Special Issue contains a selection of 16 papers covering photomultiplier tubes and silicon photomultipliers (PMTs and SiPMs) interfaces and applications [1][2][3], techniques for monitoring radiation levels [4,5], electronics for biomedical applications [6][7][8], design and applications of time-to-digital converters [9][10][11], interfaces for image sensors [12,13] and general-purpose theory and topologies for electronic interfaces [14][15][16].…”

“…Marszalek and Duda, in [ 15 ], present the design and performances of a simultaneous and multifrequency impedance measurement system used with four inductive loop sensors for detecting vehicles’ magnetic profile. Finally, in [ 16 ], Pettinato et al propose a current reference circuit based on the LT199x amplifier, which has increased accuracy and linearity with respect to commonly adopted op-amp-based solutions.…”