Differential amplifier

摘要

An amplifier for amplifying a differential audio signal, having common-mode rejection and digital gain control, includes a current source (401) which supplies a constant level of current to a first current path (I1) and a second current path (I2), and input stage (403) which modulates the current in the current paths in response to a differential input signal, and an output stage (405) which produces an output signal by amplifying the difference in current between the current paths, a degree of feedback provided to the input stage by a feedback stage (402) that modulates the current in the current paths in response to the output signal, and the degree of modulation by the feedback stage is determined by the attenuation provided by at least one multiplying digital-to-analog converter (407) located therein.

主权项

1. An amplifier for amplifying a differential audio signal having a first part and a second part, said amplifier having common-mode rejection and digital gain control, and comprising:
a first current source configured to supply a constant level of current to a first current path; a second current source configured to supply a constant level of current to a second current path; an input stage comprising:
a first transistor having a first control input to receive said first part of the differential audio signal, and configured to modulate the current in said first current path in response to said first part, anda second transistor having a second control input to receive said second part of the differential audio signal, and configured to modulate the current in said second current path in response to said second part,to produce an amplified differential signal defined by the difference in currents in said first current path and said second current path; an output stage configured to produce an output signal by amplifying said amplified differential signal; and a feedback stage comprising:
a third transistor having a third control input to receive said output signal, and configured to modulate the current in said first current path in response to said output signal,a fourth transistor having a fourth control input to receive an inverse of said output signal, and configured to modulate the current in said second current path in response to an inverse of said output signal, so as to provide a degree of feedback to said input stage, andat least one multiplying digital-to-analog converter connected with at least one of said third control input and said fourth control input, and which is configured to provide attenuation that determines a degree to which the current in said first current path and the current in said second current path are modulated by said feedback stage.