Patent ID: 6885178

Claim:
An improved headroom bandgap reference voltage circuit, the headroom being defined by a difference between the power supply voltage for the circuit and the reference voltage provided by the circuit, the circuit comprising: an operational amplifier having an inverting and a non-inverting input node, the input nodes providing a common input voltage to the operational amplifier, the operational amplifier having an output being coupled to a voltage reference node, and wherein the inverting and non-inverting input nodes are coupled to a first and a second transistor respectively, the transistors having different current densities, with one transistor operating at a first current density and the other transistor operating at a second higher current density, the transistors being configured such that the common input voltage of the operational amplifier is provided by the base emitter voltage of the transistor operating at the first current density, thereby effecting a reduction of the common input voltage of the operational amplifier so as to reduce the operational headroom of the circuit.