| 摘要 |
PURPOSE:To keep the load resistance value at a constant level despite fluctuation of the collector potential of an emitter-earthed transistor, by inserting a base-earthed transistor in series between an amplifying active element and an active load containing a constant current circuit. CONSTITUTION:The current Iref outputted from an active load 3 is divided into a current ie flowing to a base-earthed transistor TR5 and a current id flowing to an active element 7 via a level shifter 6. The sum of both currents ie and id is always kept at a constant level. While the base current ib of an amplifying active element 5 and the current flowing through the element 7 flow to a constant current circuit 8. The circuit 8 functions to keep the sum currents (ib+id) at a fixed level. As a result, the resistance value is very large when the load side is viewed from the element 1 and also kept at the constant level. Thus a high-gain state is surely maintained with a high-gain amplifier.
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