TELESCOPIC AMPLIFIER WITH IMPROVED COMMON MODE SETTLING

摘要

Telescopic amplifier circuits are disclosed. In an embodiment, a telescopic amplifier includes an input stage for receiving differential input signals, an output stage for outputting differential output signals at the drains of a first output transistor and a second output transistor, a tail current transistor coupled to sources of a first input transistor and a second input transistor, a common mode feedback circuit coupled to the differential output signals and outputting a common mode output signal, and a circuit element coupled between the common mode output signal and a gate of the tail current transistor. In an embodiment the circuit element is a resistor. In another embodiment the circuit element is a source follower transistor. In additional embodiments a phase margin of the common mode feedback open loop gain of the amplifier is determined by the value of the resistor. Additional embodiments are disclosed.

主权项

1. A telescopic amplifier, comprising:
an input stage comprising a first input transistor having a gate terminal coupled to a positive input terminal, and a second input transistor having a gate terminal coupled to a complementary input terminal; an output stage comprising a first output transistor having a source coupled to a drain of the first input transistor and having a first current source coupled to a drain of the first output transistor, and a second output transistor having a source coupled to a drain of the second input transistor, and having a second current source coupled to a drain of the second output transistor, a first output terminal coupled to the drain of the first output transistor, and a second output terminal coupled to the drain of the second output transistor, the first and second output transistor each having gates coupled to a bias voltage terminal; a tail current transistor having a drain coupled to a common source node coupled to the source of each of the first and second input transistors, having a source coupled to a ground potential, and having a gate terminal coupled to a tail gate node; a common mode feedback circuit having a first feedback input coupled to the first output terminal, and a second feedback input coupled to the second output terminal, and having a common mode reference signal input; and having a common mode output; and a resistor coupled between the common mode output and the tail gate node.