| 摘要 |
A bipolar differential amplifier having first and second transistors (Q1, Q2) and a large third transistor (Q3) sharing a common emitter resistor (Rt), and DC biasing for biasing the bases of the first, second and third transistors, whereby the first and second transistors have a DC operating current whose value I is related to the common resistor value Rt and the thermal voltage Vt by the expression Rt=Vt/2I. In this way the gain of the differential amplifier remains substantially constant over a wide range of the input signal.This produces advantages of: a wide range of linear operation, a relative low bias current may be used, and lack of noise at the central operating point introduced by the large third transistor and the emitter resistor.
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