Furthermore, the DC/DC converter having the above described con?guration may have a capability for clamping the output level (the value of the control signal 16ml) of the feedback ampli?er 1 so as not to exceed a predetermined value. One example of a feedback ampli?er having the clamping capability is illustrated in FIG. 10. In this example, the maximum value of the output level is limited to a voltage equal to or loWer than the forWard voltage of the diode.