Current sense amplifier. https://www.google.ru/search?newwindow=1&dcr=0&source=hp&ei=Vdt2Wv28C6OJmgX1w4jgCQ&q=current+sense+amplifier&oq=current+sen&gs_l=psy-ab.3.0.0l10.5322.25048.0.29723.11.10.0.1.1.0.185.1457.0j10.10.0....0...1c.1.64.psy-ab..0.11.1489...0i131k1.0.j4Cq-iGI6EI