| 摘要 |
<p>1491404 Digital-to-analogue and analogue-todigital conversion INTERNATIONAL BUSINESS MACHINES CORP 26 April 1976 [10 June 1975] 16812/76 Heading H3H [Also in Division H1] An integrated circuit for use in D/A and A/D converters comprises a CIS capacitor 23-25, Fig. 2B, and a MIC capacitor 24-26, where C is an embedded conductor 24 which is a common plate of the two capacitors. The metal M is Al and the CIS structure includes polysilicon, silicon oxide and silicon, and the ratio of the two capacitances is 1:2. The capacitances are connected together by A1 metallization 27 to form a C-2C ladder network, Fig. 1, which is used in an A/D or D/A converter using FET switches 10-15 to charge the capacitors C either to ground potential or to a reference potential V R . Each capacitor C is associated with trimming capacitors which are formed as CIS structures and which are connected selectively into circuit using laser-formed connections, to trim the capacitors C. The converter includes an AND gate 17, and a counter 19 whose output is fed back to the gates of the FET swtiches 10-15 and also provides the digital output of the converter.</p> |
