Abstract
In the process instrumentation field, conventional low level amplifiers are employing modulated carrier type DC amplifier. On the other hand, in these days, very low drift monolithic linear integrated circuits become available.
In this paper some application techniques of linear integrated circuit to 10mV DC level direct coupled amplifiers are considered.
From the theoretical analysis of non-inverting current output amplifier, thermal drift and input noise make ultimate limitation to the input signal level.
Three kinds of circuits are presented.
(i) μA 702 equiralent device applied with tiny component oven using transistor collector power dissipation as heating source.
(ii) Configuration with temperature controlled chip integrated circuit μA 727.
(iii) Configuration with dual transistor of equal VBE operation as preamplifier of integrated circuit.
From the experimental results, (i) has wide applications to field mount mV/mA converters.
(ii) has troubles of reliability and long term drift characteristics that limit the usefulness of thermal chip control. (iii) offers the most excellent low level drift characteristics and stability than the others, and has a possibility of 3mV DC input amplifier.
