Deflection with low offset

摘要

A series arrangement of a deflection coil (Lf) and a series resistor (Rs) is connected between an output of a first output amplifier (1) and an output of a second output amplifier (2) to be driven in a bridge configuration for generating a deflection current (If) through the deflection coil (Lf). Across the series resistor (Rs), a voltage is generated which corresponds to the deflection current (If). A differential amplifier (5) has a first input connected to a first end of the series resistor (Rs). A second input of the differential amplifier (5) is connected to a second end of the series resistor (Rs) via a conversion resistor (Rc). An input current (Ii) is generated through the conversion resistor (Rc). The polarity of the input current (Ii) is selected to obtain a voltage across the conversion resistor (Rc) which has an opposite polarity with respect to the voltage across the series resistor (Rs). The differential amplifier (5) has two outputs connected to respective inputs of the first and the second output amplifiers (1, 2) to drive the two output amplifiers (1, 2) in a feedback loop in such a manner that the voltage across the series arrangement of the conversion resistor (Rc) and the series resistor (Rs) is substantially zero. In this way, the voltage swing between the inputs of the differential amplifier (5) is very low and thus the offset voltage caused will be very low.