| 摘要 |
An output stage for producing a high accuracy differential output signal includes a first differential amplifier providing a pair of single-ended first signals of magnitudes that swing in opposite directions between first and second levels following a change in level of an input signal. A sum of magnitudes of the first signals is controlled by an input control current. The first signals provide input to a second differential amplifier supplying a pair of single-ended second signals swinging in opposite directions between third and fourth levels when the first signals change levels, the second signals forming the differential output signal of the output stage. An indicating signal, provided by the second differential amplifier, supplies a measure of a sum of magnitudes of the second signals. A third differential amplifier produces the control current of magnitude determined by a magnitude difference between the indicating signal and a constant reference signal. Feedback provided by the control signal ensures that the sum of magnitudes of the second signals remains constant so as to ensure that they cross a midpoint level between the third and fourth levels concurrently. The magnitude of the reference signal controls the magnitudes of the third and fourth levels in relation to the midpoint level.
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