Miles & Stockbridge P.C.
Transmission drive circuit and semiconductor integrated circuit device
Provided is a transmission drive circuit which can reduce distortions of a transmission signal and transmission noise, and is isolable from a signal line. A transmission drive circuit 700 includes a drive transistor 10 and an isolation diode 31 connected between a node n1 coupled to a signal line SL commonly used to propagate a transmission signal and a reception signal and a power source line HVP, and further includes an isolation diode 32 and a drive transistor 20 connected between the node n1 and a voltage line HVM. Furthermore, the transmission drive circuit 700 includes a switch 41 connected between a node n2 between the drive transistor 10 and the isolation diode 31, and a node n4 of a ground voltage Vs, and a switch 43 connected between a node n3 between the drive transistor 20 and the isolation diode 32, and a node n4. When the transmission signal is propagated through the signal line SL, the switches 41 and 43 are turned off by the clamp switch control circuit 200 such that bias current flows through the drive transistor 10, the isolation diode 31, the isolation diode 32 and the drive transistor 20. 
Hitachi, Ltd.
H H H B B
H03K H03K H03K B06B B06B
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Nao Satoshi Hiroyasu
Miyamoto Hanazawa Yoshizawa