| 摘要 |
PURPOSE:To make it possible to form easily a high-speed IC D/A converter by improving the structure of elements forming a current switch. CONSTITUTION:Constant-current sources 111-118 are connected to input terminals 41-48 of current switches 11-18 having digital input terminals 1-8. Respective switches 11-18 are formed as differential two-stage amplifier consisting of a pair of NPN transistors, where emitters are connected commonly into input terminals 41- 48, and a pair of PNP transistors where emitters are connected commonly. PNP transistors are formed with the vertical PNP structure on the same semiconductor substrate. By this vertical PNP structure, the cut-off frequency is enhanced, so that the switching speed of current switches can be high. Thus, a high-speed IC D/A converter can be formed easily without a special process. |
