By David Russell, reporter at OptionMonsterNEW YORK ( OptionMonster) -- Silicon Motion Technology ( SIMO) has been pulling back from a monster run, and the bulls are stepping in. OptionMonster's real-time tracking systems detected the purchase of almost 5,000 February 20 calls Wednesday against open interest of just 689 contracts. Most of them traded for 75 cents to 80 cents. These calls lock in the price investors must pay to buy shares, so they can generate major leverage if the stock moves in the right direction. But the options can also lose all their value if a rally doesn't occur before they expire at the end of next week. Silicon Motion's shares rose 1.79% to $19.30 Wednesday, down from an intraday high of $20.45. The provider of mobile chips more than doubled last year amid repeatedly strong earnings reports. It beat estimates again last week, prompting management to issue guidance above analysts' expectations. The stock tried to rally but then rolled over as investors took profits, falling from about $24 to $19. Wednesday's option activity suggested that some buyers are now returning to the name. ore than 8,300 contracts traded in total, compared with the average of about 500 in a session. Overall calls at all strikes outnumbered puts by 10 to 1. Russell has no positions in SIMO.