DAC circuit and gain adjustment method thereof

Abstract

The invention discloses a DAC circuit and a gain adjustment method thereof, the DAC circuit comprises a current mirror DIO, a slope generation circuit and an output resistance circuit, the current mirror DIO adopts a multi-gear parallel structure, the output resistance circuit adopts a multi-resistor parallel structure, the current mirror DIO and the output resistance circuit are both integrated with switches, and the slope generation circuit is connected with the current mirror DIO. And the two control modules are respectively used for controlling the parallel connection number of the MOS tubes and the parallel connection number of the resistors of the current mirror DIO. The gain adjustment method adopts a gain linkage adjustment mode, the overall design is simple and ingenious, the layout area can be reduced, the cost is saved, the current source tube of the slope generation circuit is ensured to be always in a saturation region when the DAC is in gain switching, and the gain adjustment range of the DAC is greatly improved.

Description

technical field [0001] The invention relates to the field of integrated circuits, in particular to a DAC circuit and a gain adjustment method thereof. Background technique [0002] In a very dark shooting environment, the effective image signal is very weak, in order to achieve the specified video amplitude or image brightness, it is necessary to increase the gain of the system. [0003] For the ADC of the Pipeline architecture, its gain is mainly controlled by adjusting the voltage amplitude of the DAC output ramp. [0004] For a current-steering DAC, the change in current at 24dB gain is 1 / 16 times that of 0dB. Since the current changes too much, the saturation margin of the current source tube of the ramp generation circuit will be insufficient, or the current source tube will be directly moved from the saturation region to the non-saturation region. [0005] If the saturation margin of the current tube is insufficient or enters the non-saturation region, the power supp...

AI Technical Summary

Problems solved by technology

Due to the large current change, the saturation margin of the current source tube of the slope generating circuit will be insufficient or the current source tube will directly enter the unsaturated area from the saturated area.

[0005] If the saturation margin of the current tube is insufficient or enters the non-saturation region, the power supply rejection ratio and slope linearity of the DAC will be poor, and the slope at high gain cannot be used normally. Therefore, the gain of the current tube after entering the non-saturation region is unavailable

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