| 摘要 |
<p>PURPOSE:To make small the unit size and to increase the reliability, by making easy circuit integration and the improvement of characteristics, through the use of operational amplifier for the communication current supply circuit. CONSTITUTION:The terminals 1, 2 connected to a pair of telephone lines and the terminals 3, 4 connected to the power supply or ground are provided, and to the electronic circuit connected between the terminals 1 and 3, the series connection between the parallel circuit of the first resistor 7 and the first capacitor 21 and the parallel circuit of the second resistor 5 and the second capacitor 19 are connected. Further, to the junction of the parallel circuits, one input terminal of the operational amplifier 15 is connected via the third resistor 13, and the output of the amplifier 15 is connected to the base of the transistor Tr9. The emitter of Tr9 is connected to another input of the amplifier 15 via the fourth resistor 17 and connected to the terminal 3 via the resistor 11, and the collector is connected to the terminal 1. Further, the operational amplifier 16 of the similar circuit constitution is located between the terminals 2 and 4, the amplifiers 15, 16 are connected by the capacitor 23 to increase the characteristics by increasing the differential AC impedance between the terminals 1, 3 and 2, 4.</p> |
