Low GM transconductor

摘要

Techniques for designing a transconductor configurable to have a low transconductance. In one aspect, a voltage to current conversion module is coupled to a 1:N current replication module. The voltage to current conversion module may be implemented as an operational amplifier configured with negative feedback to generate a current through a transistor, wherein such current is proportional to the difference between an input voltage and a common-mode reference. The 1:N current replication module is configured to mirror the generated current in another transistor, to a predetermined ratio, such that the output current is also proportional to the difference between the input voltage and the common-mode reference. In exemplary embodiments, the output stage driving the output current may be configured to operate as a Class A, Class B, or Class AB type amplifier.

主权项

1. An apparatus comprising:
an operational amplifier configured to set a gate voltage of an input transistor to generate a current, the current comprising a component proportional to an input voltage minus a reference voltage; a resistor coupling the input voltage to an input of the operational amplifier, the resistance of the resistor defining the proportionality between the component current and the input voltage minus the reference voltage; and a current replication module configured to replicate the current at a 1:N ratio to generate a transconductance current proportional to the input voltage, the current replication module comprising: a first transistor having a predetermined size ratio relative to the input transistor, the gate voltage of the input transistor being coupled to the gate voltage of the first transistor; the transconductance current being derived from the drain current of the first transistor; and the current of the input transistor further comprising an input bias current, the first transistor being biased by a first bias current, the first bias current having the same predetermined size ratio relative to the input bias current as the first transistor has relative to the input transistor.