PURPOSE: To widen the dynamic range, by inserting a resistor to a base current absorbing part of a constant current load.
CONSTITUTION: When setting of 700(mV)<Vref≤Vcc is set, where Vcc is a voltage of a constant voltage source 12 and Vref is a voltage of a reference voltage source 13 and when an input voltage Vin is gradually increased from 0(V), transistors (TR) 2, 9, 11 turn on at 0<Vin ≤Vref, and the output is at "L". Taking the current of a constant current source 3 as I 0 , TRs 1, 2 have a current of about I 0 /2 at Vin=Vref with a good balance and the TRs 2, 9, 11 turn off from on and the TRs 1, 4 turn on from off as transient state. The TRs 1, 4 turn on and the TRs 2, 9, 11 at Vin>Vref and the output is at "H". A resistor 15 is inserted to a base current absorbing section to prevent the saturation of the TR1 at Vin=Vcc.