The greenback was mildly weaker versus the yen around 102 yen, down 0.20 percent on the day. This followed a choppy session on Friday where the dollar managed a 0.2 percent gain against the safe-haven Japanese currency, rebounding from an initial sell-off due to data that showed a second straight month of below-forecast jobs growth.
The euro was flat against the dollar near $1.36 and fell 0.14 percent against the yen near 139 yen.
While analysts anticipate U.S. lawmakers will question Yellen, the first female head of the Fed, on subjects from monetary policy to bank regulations, they reckon she will stick to replies that would not alter expectations the Fed will hold short-term rates near zero for an extended period to support the economy.
Nor do analysts foresee she would say anything to upset expectations the Fed will back away from its tapering of its massive bond-purchase stimulus even after news U.S. employers added only 113,000 workers last month, far fewer than the 185,000 increase forecast by analysts.
The Fed has reduced its third round of quantitative easing twice, to $65 billion in February and Wall Street widely expects monetary policy-makers to taper by another $10 billion a month at their March meeting.
In other G10 currency action, Norway's crown advanced against the euro and dollar after higher-than-expected inflation was read as eliminating the chances of an interest rate cut.
Georg Von Wowern from Scandinavian bank Nordea said Norway's central bank would look past the inflation numbers, which were influenced by post-Christmas sales. But he said the crown, which fell almost 15 percent last year against the euro, had been looking oversold and may have room to regain more ground.
The crown rose about 0.5 percent from Friday versus the dollar and euro at 6.14 crowns to the dollar and 8.37 crowns per euro.
For more information on foreign exchange, please click here.