Виктор писал(а):
82
Операционный усилитель средней точности
Может и средней. Но термостабильность должна быть на высоте, слева - четверка симметричных и запараллеленных крест-накрест транзисторов входного дифкаскада. Вероятно - это копия uA725.
OP AMP APPLICATIONS. Walter G. Jung писал(а):
There are some circuit subtleties belied by the schematic's simplicity, but yet important. Q1 and Q2 are actually a quad set (dual pairs), with the paralleled pairs straddling the chip's axis of thermal symmetry. The idea behind this was that thermal changes due to output stage dissipation would be seen as equal thermally induced offsets by the two input stage halves, and thus be rejected. This principle, first established in the 725 design, has since become a basic precision design principle (see Reference 15, again, and within Reference 23, the Fig. 2 chip photograph).
Another key point of 725 performance optimization concerns offset nulling for a condition of zero input offset and lowest drift, described in some detail by Erdi within References 23 and 24. The 725 had a typical offset voltage spec of 600μV, and with the offset nulled as recommended, the resulting drift was 0.6μV/°C. The bias current was typically 45nA, and open-loop gain was 132dB.
Фотку по ссылке, правда, найти [пока] не удалось.