High linearity CMOS analogue switch suitable for low voltage
A technology of analog switch and sampling switch, which is applied in the field of high linearity CMOS analog switch, can solve problems affecting circuit linearity, affecting input signal swing, 16-point voltage limit, etc., to eliminate the limitation of circuit function and realize normal operation , Improve the effect of linearity
Inactive Publication Date: 2009-11-04
FUDAN UNIV
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Problems solved by technology
Two main problems can be seen from the expression: First, the highest level of the input signal must be lower than the gate voltage of the MOS transistor by a threshold voltage (V THN ) to turn on the switch, which will seriously affect the swing of the input signal as the power supply voltage continues to decrease; secondly, the on-resistance of the switch will increase with the gate-source voltage of the MOS tube (V dd -V in ) and threshold voltage V THN And changes, which directly affect the linearity of the entire circuit, making it unable to meet the requirements of today's high-precision circuits
However from figure 2 It can be seen that the voltage at node 17 is always higher than the voltage at node 16 (ie, V in ) is a higher threshold voltage, due to the limited output swing of the operational amplifier 6, the voltage at point 16 is severely limited, making it impossible to use a large swing input signal
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[0026] Further describe the present invention below in conjunction with accompanying drawing.
[0027] exist Figure 4 Among them, resistors 36 and 38 have the same resistance value, which is much larger than the resistance value of resistor 37. input signal V in After being divided by resistors 37 and 38, a voltage approximately equal to V is generated at node 60 in The signal of is used as the input of the positive terminal of the operational amplifier 56. Operational amplifier 56 and replica sampling switch 39 form a negative feedback circuit, so that the voltage at node 59 is equal to the voltage at node 60, that is, approximately equal to the input signal V in , so the replica sampling switch 39 works in the deep linear region, which is consistent with the state of the sampling switch 40 . By adjusting the resistance values of the resistors 36, 37 and 38, the drain-source voltages of the replica sampling switch 39 and the sampling switch 40 can be substantially equa...
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The invention belongs to the technical field of integrated circuits, in particular to a high linearity CMOS analog sampling switch suitable for low voltage. It consists of 3 voltage divider resistors, 1 operational amplifier, 1 replica sampling switch, 1 sampling switch, 1 pseudo sampling switch, and 2 boost circuits. A negative feedback circuit is formed by the operational amplifier and the replica sampling switch, thereby replicating the same threshold voltage as the sampling switch for the replica sampling switch. Then, the gate voltage of the replica sampling switch is used as the control signal of the sampling switch to eliminate the variation of the on-resistance of the sampling switch with the input signal and the threshold voltage, thereby greatly improving the linearity of the sampling switch. At the same time, two boost circuits are used to eliminate the limitation of the output swing of the operational amplifier on the circuit function, and realize the normal operation under low voltage.
Description
technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a high-linearity CMOS analog switch suitable for low voltage. Background technique [0002] In today's mixed-signal integrated circuit design field, switched capacitor circuits are playing an extremely important role. In the past, resistors were often used in circuits, but it is difficult to precisely control the resistance of resistors in CMOS technology, so the accuracy of the circuit will be greatly restricted. In contrast, it is easier to realize accurate capacitance, so switched capacitor circuits can achieve higher accuracy. In addition, the switched capacitor circuit utilizes the principle of charge storage, so it has a larger dynamic range and better temperature characteristics. With its many advantages, switched capacitor circuits have been widely used in audio modulation, baseband signal processing of wireless transceivers and other systems. A...
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IPC IPC(8): H03K17/14H03K17/16H03K17/687G11C27/02
Inventor 彭云峰严伟周锋
Owner FUDAN UNIV