In previous VFC type A/D converter high linearity charateristics knave been achieved to several hundred kHz, and in the converter with maximum output frequency of several MHz, the conversion linearity is poor in upper frequency range. In this paper the problem of the extension of the output frequency to MHz range is studied in the following two view points: First, a tunnel diode VCO is used to increase the output frequency range to several MHz. Second, the linearity between the input voltage and the frequency of the output pulse is accomplished by using negative pulse feedback circuit. From the experimental results, it was followed that the linearity of the proposed converter was about 0.209 percent at the frequency of 3.7MHz.