Patent ID: 6842066

Claim:
A bias circuit which supplies a bias voltage to a first transistor, comprising: a second transistor formed on a same semiconductor substrate as the first transistor and having a control electrode and a first and a second main electrodes; a first constant resistance; and a first and a second level shifters, the second transistor being either a metal semiconductor field effect transistor or a high electron mobility transistor, one end of the first constant resistance being connected to a first voltage supply, other end of the first constant resistance being connected to the first main electrode of the second transistor, the control electrode of the second transistor being connected to the second main electrode of the second transistor, the second main electrode of the second transistor being connected to a second voltage supply lower than the first voltage supply, a voltage at the first main electrode of the second transistor being divided by the first and second level shifters and the divided voltage being outputted as the bias voltage.