| 摘要 |
PURPOSE:To contrive the saving a power consumption by constituting the tilted circuit in which a prescribed voltage is applied to the reference input terminal of an operational amplifier constituting a constant current circuit when a line resistance is a prescribed value or below. CONSTITUTION:When the line resistance is large, an applied voltage to resistors RA1, RB2 and a current conduced through the lines A, B is small. When the line resistance is small, a voltage between the line A and a power supply section (-48V) or between the line B and a jumper terminal G (or +50V), the applied voltage to the resistors RA1, RB1 is large and the line current is increased. In such a case, a base current is conducted to transistors (TRs) QA1, QB1. As a result, the emitter voltage of the TRs QA1, QB1 is constant. That is, the line resistance is a prescribed value or below, the noninverting input voltage to the operational amplifiers ICA, ICB constituting the constant current circuit is constant and then the line current is made constant. In limiting the current in such a manner, the power consumption is reduced. |
