Startup Circuit for Reference Circuits

摘要

A start-up circuit for a reference circuit such as a bandgap reference circuit. The start-up circuit includes a diode-connected metal-oxide-semiconductor (MOS) transistor connected between a power supply node and a start-up node that is connected in turn to the gate of a current control MOS transistor in the reference circuit. The diode-connected MOS transistor and the current control MOS transistor are matched with one another. To start up the reference circuit, current is conducted through the diode-connected MOS transistor to set the gate voltage of the current control transistor at a threshold voltage below the power supply voltage. Current conducted by the current control transistor initiates operation of the bandgap reference circuit, and disables the start-up circuit.

主权项

1. A circuit for generating a reference level, comprising:
a reference circuit, comprising:
a primary current branch, comprising a current control transistor having a source-drain path coupled on one side to a power supply voltage, and having a gate;an amplifier having inputs coupled to nodes in the primary current branch, having an active load comprising a current mirror including a mirror transistor having a conduction path coupled between a power supply voltage and an amplifier output node, the amplifier output node also coupled to the gate of the current control transistor; anda first output transistor conducting a first reference current responsive to a voltage at the amplifier output node; and a start-up circuit, comprising:
a start-up transistor having a source coupled to the power supply voltage, and having a gate and a drain connected together at a start-up node coupled to the amplifier output node, the start-up transistor constructed in a matching manner relative to the current control transistor; anda first current source coupled between the start-up node and a ground reference voltage.