| 摘要 |
PURPOSE:To eliminate the unstable operation of a comparator consisting of an N-MOS and to realize highly precise conversion, by setting the first comparing reference potential of a successive comparison type A/D converter at 3/4 reference voltage. CONSTITUTION:An anlog input 24 of a successive comparison type A/D converter turns on S1, S2 and S4 and is sample-held at a capacitor C1. Then S1, S3 and S4 are turned off with the S2 turned on, and the comparison with the reference potential 22 is carried out through a comparator 2 consisting of amplifiers Tr1 and Tr2 of an N-MOS. Then the output 23 is successively fed to a comparison controlling part to change the reference potential. The own bias of the Tr1 is set at 1.4V, and the comparing reference potential is set 3/4 reference voltage 5V with an input set at 5V. Thus the potential of a terminal C11 is set at 1.4-(5-3.75)V and positive. As a result, a forward current produced by a p-n junction does not flow to realize the use of an amplifier of high gain. In such way, a conversion is possible with high precision. |
