| 摘要 |
The protection circuit 8 has first and second input terminals 10, 11 connected to the operating power supply voltage of a user device 9 and to ground respectively, and a terminal 12 receiving an input signal voltage of varying magnitude and connected to an output terminal 13 via a node 14. A diode 15 is connected between input terminals 10, 11, a MOSFET 16 has drain and source electrodes 17, 18 coupled to node 14 and terminal 10 respectively, and a bipolar transistor 20 has its emitter 21 and collector 22 coupled to node 14 and terminal 11 respectively with its base 23 coupled to N-well substrate 24 of MOSFET 16. The transistors 16, 20 and the diode 15 provide conduction paths in the event of excess voltage occurring at the signal input terminal 12 and so provide voltage protection at the output terminal 13. The circuit 8 may be constructed from a low number of components on a single integrated circuit, the transistor 20 being formed as a parasitic element of the MOSFET 16, and the diode 15 being formed by the N-well 24 of the MOSFET 16. <IMAGE> |
