Context : The VLT-FLAMES Tarantula Survey has observed hundreds of O-type stars in the 30 Doradus region of the Large Magellanic Cloud ( LMC ) .

Aims : We study the properties of a statistically significant sample of O-type dwarfs in the same star-forming region and test the latest atmospheric and evolutionary models of the early main-sequence phase of massive stars .

Methods : We performed quantitative spectroscopic analysis of 105 apparently single O-type dwarfs .
To determine stellar and wind parameters , we used the iacob-gbat package , an automatic procedure based on a large grid of atmospheric models that are calculated with the fastwind code .
This package was developed for the analysis of optical spectra of O-type stars .
In addition to classical techniques , we applied the Bayesian bonnsai tool to estimate evolutionary masses .

Results : We provide a new calibration of effective temperature vs. spectral type for O-type dwarfs in the LMC , based on our homogeneous analysis of the largest sample of such objects to date and including all spectral subtypes .
Good agreement with previous results is found , although the sampling at the earliest subtypes could be improved .
Rotation rates and helium abundances are studied in an evolutionary context .
We find that most of the rapid rotators ( v sin i > 300 km s ^ { -1 } ) in our sample have masses below \sim 25 M _ { \odot } and intermediate rotation-corrected gravities ( 3.9 < log g _ { c } < 4.1 ) .
Such rapid rotators are scarce at higher gravities ( i.e .
younger ages ) and absent at lower gravities ( larger ages ) .
This is not expected from theoretical evolutionary models , and does not appear to be due to a selection bias in our sample .
We compare the estimated evolutionary and spectroscopic masses , finding a trend that the former is higher for masses below \sim 20 M _ { \odot } .
This can be explained as a consequence of limiting our sample to the O-type stars , and we see no compelling evidence for a systematic mass discrepancy .
For most of the stars in the sample we were unable to estimate the wind-strength parameter ( hence mass-loss rates ) reliably , particularly for objects with lower luminosity ( \log { L / L _ { \odot } } \lesssim 5.1 ) .
Only with ultraviolet spectroscopy will we be able to undertake a detailed investigation of the wind properties of these dwarfs .

Conclusions :