The key Indian equity indices traded on a flat note amid a choppy trade on Thursday morning.Around 10.20 a.m., Sensex was trading at 37,909.98, higher by 38.46 points or 0.10 per cent from the previous close of 37,871.52.It opened at 37,814.92 and touched an intra-day high of 37,969.60 and a low of 37,738.59 points.The Nifty50 on the National Stock Exchange was trading at 11,161.50, higher by 28.90 points or 0.26 per cent from its previous close.Among the stocks, Yes Bank shares on the BSE touched the 20 per cent lower circuit as it fell to Rs 14.60 per share during the initial trade.Currently, its trading at Rs 16, lower by Rs 2.25 or 12.33 per cent from its previous close.