| 摘要 |
<p>PURPOSE:To obtain a compact an inexpensive telephone current supply circuit by securing the common connection between both feedback points of a DC feedback circuit of 1st and 2nd constant current circuits and using each collector output of transistors (TRs) as the telephone current supply output. CONSTITUTION:A 1st constant current circuit contains a uni-conducting transistor TRQ1, a base bias circuit R12 of the TRQ1, and a DC feedback circuit R11 led to the circuit R12 from the collector of the TRQ1. While a 2nd constant current circuit includes a reverse conducting TRQ2, a base bias circuit R22 of the TRQ2, and a DC feedback circuit R21 led to the circuit R22 from the collector of the TRQ2. Then the common connection is secured between both feedback points B of circuits R11 and R21 respectively and each collector output of both TRQ1 and Q2 is used as the telephone current supply output. Thus a telephone current supply circuit consists of only the TRQ1 and Q2 and resistance elements R11-R14 and R21-R24 and can be transformed into an IC to remarkably realize a compact and inexpensive structure.</p> |
