Analysis of Operational Amplifier Circuit of High Gain CMOS Differential Amplifier

Figure 3.4-7 is a high-gain two-stage CMOS operational amplifier. In order to increase the gain, the load of the input stage (differential amplifier) adopts the high-impedance current source circuits M3∧, M4∧, M3 and M4 introduced in the second section of Chapter 2 as loads, and a common gate circuit (M1 ∧ and M2∧), thereby increasing the output impedance of the differential amplifier. High gain CMOS. In this way, as the input stage of the differential amplifier, its voltage gain is an order of magnitude higher than the voltage gain of the general form of the differential amplifier. Therefore, the voltage gain of the circuit can reach more than 10,000 times. The M7 tube in the picture is used as a level shift circuit,Common source amplifier circuit for the output stage. In order to ensure that the differential pair tube M1 and M2 work in the saturation region, the aspect ratio of M9 should be selected appropriately.

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