ELECTRIC CURRENT CONVERTING CIRCUIT

摘要

PURPOSE:To simplify the constitution of a mode changeover switch by obtaining electric currents representing combinations of plural modes by combining and connecting with each other plural differential amplifiers. CONSTITUTION:The 1st and 2nd differential amplifiers DA1-DA2 having different offset are provided in an electric current converting circuit and input sections composed of transistors (TR) Q3 and Q5 and Q8 and Q10 are respectively installed to the amplifiers DA1 and DA2. An input voltage is inputted in the amplifiers DA1 and DA2 by commonly connecting the amplifier DA2 with the amplifier DA1 through diodes Q6 and Q7 and connecting a switch SW1 with the common point. Moreover, a differential amplifier DA3 equipped with TRs Q21 and Q22 is provided to the amplifiers DA1 and DA2 and a current mirror circuit is constituted of the amplifiers DA1-DA3 and a constant current. Then an A-mode output current is outputted from a TRQ18 and B-mode output current is outputted from the TR22. Thus the constitution of a mode change-over switch is simplified.