| 摘要 |
<p>A digital-to-analog converter (30) has two power supply nodes (N30/ N32) connected through a ladder-type resistor network (31) to n-p-n bipolar transistors (34a/ 35a/36a/37a) supplied with a reference voltages (Vref) and directly supplied to n-p-n bipolar transistors (34a/ 35a/ 36a/37a) responsive to a digital input signal (D1- D4), respectively, when a manufacturer tests the digital-to-analog converter (30), the tester (38) sequentially changes the value of the digital input signal (D1-D4), and an ammeter (39) measures the amount of electric current flowing through the ladder-type resistor network (31) into the n-p-n bipolar transistors (34b/ 35b/ 36b/ 37b) for accurately diagnosing the digital-to-analog converter on the basis of the variation of the electric current. <IMAGE></p> |
