| 摘要 |
<p>A bi-CMOS output circuit composed of a combination of bipolar transistors and a CMOS circuit has a current path of two bipolar transistors connected in series between the power source and ground. When the grounded bipolar transistor is driven by the other bipolar transistor, the output current can be guaranteed when the output voltage is low. When the output voltage is high, however, a large current flows into the bipolar transistor, thereby causing the power source voltage to vary. Therefore, the control input of the grounded bipolar transistor (Q12) is connected to the output terminal of an MOS transistors (M11) through a resistor (R12). In this manner, the grounded bipolar transistor (Q12) is driven by the MOS transistor which has less capability than ordinary bipolar transistors. Therefore, a predetermined current is guaranteed when the output voltage is low, and excessive current is prevented from flowing when the output voltage is high.</p> |
