All digital transistor high gain operational amplifier using positive feedback technique
AssigneeTexas Instruments Incorporated
InventorMezyad Amourah
Life of this patent
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Abstract
A new all digital transistor CMOS very high DC-gain amplifier (30) that uses an internal positive-feedback technique. This amplifier (30) does not require perfect matching of transistors (M2,M3) to achieve the very high DC gain. The DC gain has a very low sensitivity to the output voltage swing. An implementation of a sample and hold circuit (60) constructed using the amplifier (30) is also described. A special layout pattern (80) is used to cut the parasitic capacitance to enhance the amplifier speed.
Claims10
An operational amplifier, comprising:
- a telescopic cascoded amplifier having differential input transistors and an output providing an output signal;
- and
- a feedback circuit coupled to the amplifier output and providing positive feedback to the amplifier, the positive feedback being self-adjusting,
- wherein the telescopic cascaded amplifier has multiple transistors forming multiple nodes, wherein the positive feedback is derived from the multiple nodes
- wherein the multiple transistors have a chopped diffusion layout to reduce diffusion parasitic capacitance while increasing sidewall capacitance.
An operational amplifier, comprising:
- a telescopic cascoded amplifier having differential input transistors and an output providing an output signal;
- and
- a feedback circuit coupled to the amplifier output and providing positive feedback to the amplifier, the positive feedback being self-adjusting,
- wherein the feedback circuit is maintained to be substantially unaffected by a varying output voltage signal of said output signal.
An operational amplifier, comprising:
- a telescopic cascoded amplifier having differential input transistors and an output providing an output signal;
- and
- a feedback circuit coupled to the amplifier output and providing positive feedback to the amplifier, the positive feedback being self-adjusting.
- wherein the open loop gain of the amplifier is defined by the equation:
- A v = - g m1 · ( g o2 · g m2 ) g o1 [ g o2 g o3 g m3 ] ( g o4 g o1 + 1 ) - g o1 g o2
- where:
- gm1 is the conductance of the differential input transistors;
- gm2, gm3 is the conductance of multiple transistors forming the multiple nodes;
- g01 is the gain of the differential input transistors;
- and
- g02, g03 is the gain of the multiple transistors forming the multiple nodes.
An operational amplifier, comprising:
- a telescopic cascoded amplifier having differential input transistors and an output providing an output signal;
- and
- a feedback circuit coupled to the amplifier output and providing positive feedback to the amplifier, the positive feedback being self-adjusting,
- wherein the amplifier is comprised of all MOS transistors, wherein the amplifier is not strobed.
Dependencies are inferred from the claim text.