Patent ID: 7173407

Claim:
A voltage circuit including a first amplifier having first and second inputs and having an output driving a current mirror circuit, outputs from the current mirror circuit driving first and second n-type bipolar transistors which are coupled to the first and second input of the amplifier respectively, the base of the first n-type transistor being coupled to the second input of the amplifier and the collector of the first transistor being coupled to the first input of the amplifier such that the amplifier keeps the base and collector of the first transistor at the same potential, the second n-type transistor being provided in a diode configuration, and wherein the first and second n-type transistors are adapted to operate at different current densities such that a difference in base emitter voltages between the first and second n-type transistors may be generated across a resistive load coupled to the second n-type transistor, the difference in base emitter voltages being a PTAT voltage, the circuit additionally including first and second p-type bipolar transistors, the first p-type transistor being provided in a feedback configuration between the output node of the amplifier and the inverting input of the amplifier, the second p-type transistor being provided in a diode configuration with the base and collector being commonly coupled via the resistor to the second n-type transistor, the base of the first p-type transistor being coupled to the base of the first n-type transistor and also to the inverting input of the amplifier, the collector of the first p-type transistor being coupled to the collector of the first n-type transistor and also to the non-inverting input of the amplifier, the arrangement of the first p-type and first n-type transistors providing a pre-amplification of the signal prior to the amplification provided by the amplifier.