Design Of High-speed And High-accuracy Track-and-Hold Circuit Based On 0.18μm CMOS Technology

The Track-and-Hold circuit, which is one of the key components of many analog and Mixed-signal IC circuits, is widely used in ADC, CMOS switch-capacitor filter, integrator and so on. In the ADC, as the first module in the whole signal processing chain, the Track-and-Hold circuit directly determines the performance of the entire ADC. Therefore, designing a high-speed, high-precision Track-and-Hold circuit, seems particularly important.The work of this thesis is the design of 9-Bit 1Gsps high-speed Track-and-Hold circuit with sampling error 1.4783mV and 14-Bit 100Msps high-accuracy Track-and-Hold circuit with sampling error 46.8846μV and SFDR(Spurious Free Dynamic Range)91dB when input frequency is 47.94MHz based on SMIC 0.18μm CMOS process. Open-loop structure uses dummy switch, common source buffer, as well as differential circuits, these circuit restrain the clock feed-through effects effectively, the differential circuit has the advantage of reduce the effect of the sampling accuracy caused by charge injection. Closed-loop structure uses Flip-around sample-and-hold circuit because of its noise and precision advantages, and uses a new type of high-precision sampling switch (the switch uses comparator, inverter, CMOS switches and capacitors to achieve high linearity), in order to ensure the accuracy of sampling, designs a Gain-boosted folded cascode operational amplifier to ensure the requirements of high-gain and bandwidth of the OPA. CMFB uses switched-capacitor structure, and it has the advantage of the OPA output voltage swing will not be limited by common-mode voltage feedback circuit, and because it is completely composed of passive devices (capacitor) and the switches, there is no direct current power in this circuit. Comparator uses differential structure with positive and negative resistance as load.These circuits adopt SMIC 0.18μm CMOS technology with VDD 1.8V. Finally, analyzes the performance and simulates the circuit using the Cadence Spectre. The results show that the circuit meets the design requirements with good performance.