| 摘要 |
PURPOSE:To obtain a handset amplifier circuit whose minimum ON voltage is made small while its maximum undistorted power output is enlarged, by using a common- emitter transistor at the output stage. CONSTITUTION:A power voltage supplied between output terminals 1 and 2 is smoothed by resistance R5 and capacitor C1. The smoothed voltage across capacitor C1 is voltage-divided by resistances R1 and R2 into two; one is the operating-point voltage of operational amplifier A1, and the other is its output voltage. The base current of transistor Q3 is absorbed with the variation in current flowing into emitter-follower Q2, so that a current flowing to resistance R5 will not vary. Therefore, the voltage across capacitor C1 and the voltage between output terminals 1 and 2 become constant without having relation to the DC amplification factor of emitter- common transistor Q3. |
