CMOS voltage bandgap reference with improved headroom
First Claim
Patent Images
1. 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.
1 Assignment
0 Petitions
Accused Products
Abstract
A voltage bandgap reference voltage circuit is provided. The circuit includes an amplifier having a first and second transistor coupled to the inputs of the amplifier. The circuit is adapted to operate with lower headroom by effecting a subtraction of a voltage substantially equivalent to Delta Vbe of the first and second transistors from the voltage applied to the common input of the amplifier.
47 Citations
12 Claims
-
1. 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
- 10. A bandgap reference voltage circuit having an operational amplifier with a first and a second transistor coupled to first and second inputs thereof, the first and second transistors having different current densities, the first transistor operating at a first current density and the second transistor operating at a second higher current density, the operational amplifier having a common input voltage, and wherein a resistor is provided between a first input of the operational amplifier and the second transistor, such that the voltage at the common input to the operational amplifier is lower than the base-emitter voltage of the second transistor by an amount substantially equivalent to the base-emitter voltage difference of the two transistors.
-
12. A method of providing a voltage bandgap circuit with improved headroom, the method comprising the steps of:
-
providing an amplifier having first and second inputs and having a common input voltage, with transistor components coupled to the inputs, the transistor components being provided with different current densities, with a first transistor components operating at a first current density lower than the current density of the second transistor components, the transistor components being configured to generate a bandgap voltage at the common input voltage of the amplifier, effecting a reduction of the voltage applied to the common input by an amount substantially equivalent to a difference in base emitter voltages of the transistor components coupled to the inputs of the amplifier, the reduction being effected by the provision of a resistor between a first input of the amplifier and the second transistor components.
-
Specification