抄録
In this paper, a new method to improve the differential linearity of Successive Approximation type AD Converter (S.A.A.D.C.) is described.
The S.A.A.D.C. has very short conversion time and is widely used, but has very poor channel width uniformity. For this reason, the S.A.A.D.C. is scarcely used for the measurement of Probability Density Function (P.D.F.) of every random signals. Especially, AD converter (A.D.C.) for the radiation Pulse Height Analyzer (P.H.A.) (Rundom pulse amplitude distribution analyzer) must have good differential linearity. Run-down type A.D.C. which is first proposed by Wilkinson gives excellent differential linearity, but is applicable only to the P.H.A..
The largest cause for the channel width irregularity of S.A.A.D.C. is due to the channel width irregularity of the DA converter (D.A.C.) used in it.
A special feature of this proposed method is that a plural D.A.C. is used in the S.A.A.D.C.. Output signals of these D.A.C.s are averaged to obtain the uniform channel width of S.A.A.D.C..
In the first parts of this paper, the principle of this method is shown. In the second parts, the channel equalizing effect of this method is analyzed using the correlation moment. In the final parts, the validity of this method is examined by the following measurements.
1) The P.D.F. of the uniformly distributed continuous random signal is measured.
2) The pulse height distribution of the gamma rays (60Co) detected by scintillation detector is measured.
Through these tests, it is confirmed that this method has good faculty of channel equalization on S.A.A.D.C..
