Band gap reference using a low voltage power supply
First Claim
1. A band gap reference comprising:
- an operational amplifier (opamp) having a (+) input, a (-) input, and an output;
a first diode having a first terminal coupled to VSS, and a second terminal coupled to the (+) input of the opamp;
a first current source transistor having a source to drain path coupling VDD to the second terminal of the first diode, and a gate coupled to the output of the opamp;
a second diode having a first terminal coupled to VSS, and a second terminal;
a first resistor having a first terminal coupled to the second terminal of the second diode, and a second terminal coupled to the (-) input of the opamp;
a second current source transistor having a source to drain path coupling VDD to the second terminal of the first resistor, and a gate coupled to the output of the opamp;
a third diode having a first terminal coupled to VSS, and a second terminal;
a second resistor having a first terminal coupled to the second terminal of the third diode, and a second terminal providing the output of the band gap reference; and
a third current source transistor having a source to drain path coupling VDD to the second terminal of the second resistor, and a gate coupled to the output of the opamp.
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Accused Products
Abstract
A band gap reference includes an operational amplifier with an output (n23) driving the gate of three current source transistors (501-503). The first current source (501) drives the (+) opamp input (n20) and a transistor (511) functioning as a diode. The second current source (502) drives the (-) opamp input and a series resistor (R1) and a transistor (512) functioning as a diode. The third current source (503) drives a series resistor (R2) and diode connected transistor (513). The opamp includes first series transistors (521) and (524) connected between VDD and VSS, and second series transistors (522) and (525) connected between VDD and VSS. With only two series transistors between VDD and VSS at any point, only two times a CMOS transistor threshold drop (less than 1.8 volts) will occur enabling VDD to range from 1.8-3.6 volts without altering the band gap reference output voltage (VDIODE). Further, CMOS transistors in the circuit may operate with a 2.7 volt maximum gate to source, or gate to drain voltage.
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Citations
17 Claims
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1. A band gap reference comprising:
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an operational amplifier (opamp) having a (+) input, a (-) input, and an output; a first diode having a first terminal coupled to VSS, and a second terminal coupled to the (+) input of the opamp; a first current source transistor having a source to drain path coupling VDD to the second terminal of the first diode, and a gate coupled to the output of the opamp; a second diode having a first terminal coupled to VSS, and a second terminal; a first resistor having a first terminal coupled to the second terminal of the second diode, and a second terminal coupled to the (-) input of the opamp; a second current source transistor having a source to drain path coupling VDD to the second terminal of the first resistor, and a gate coupled to the output of the opamp; a third diode having a first terminal coupled to VSS, and a second terminal; a second resistor having a first terminal coupled to the second terminal of the third diode, and a second terminal providing the output of the band gap reference; and a third current source transistor having a source to drain path coupling VDD to the second terminal of the second resistor, and a gate coupled to the output of the opamp. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A band gap reference comprising:
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an operational amplifier (opamp) having a (+) input, a (-) input, and an output, the opamp comprising; a first transistor (524) having a gate forming the (+) input of the opamp; a second transistor (525) having a gate forming the (-) input of the opamp, and a source to drain path connected on a first end to a first end of the source to drain path of the first transistor (524); and a current mirror comprising; a third transistor (521) having a source to drain path coupling VDD to a second end of the source to drain path of the first transistor (524), and having a gate; and a fourth transistor (522) having a source to drain path coupling VDD to a second end of the source to drain path of the second transistor (525), and having a gate coupled to the gate of the third transistor (521); a current sink having a first terminal coupled to VSS, and a second terminal coupled to the first end of the source to drain path of the first transistor (524) and the second transistor (525); a first bipolar transistor (511) having an emitter to collector path coupling the (+) input of the opamp to VSS, and a base coupled to the second terminal of the current sink; a first current source transistor (501) having a source to drain path coupling VDD to the (+) input of the opamp, and having a gate coupled to the output of the opamp; a first resistor (R1) having a first terminal coupled to the (-) input of the opamp, and a second terminal; a second bipolar transistor (512) having an emitter to collector path coupling the second terminal of the first resistor (R1) to VSS, and a base coupled to the base of the first bipolar transistor (511); a second current source transistor (502) having a source to drain path coupling VDD to the (-) input of the opamp, and having a gate coupled to the output of the opamp; a second resistor (R2) having a first terminal forming the output of the band gap reference, and a second terminal; a third bipolar transistor (513) having an emitter to collector path coupling the second terminal of the second resistor (R2) to VSS, and having a base coupled to VSS ; and a third current source transistor (503) having a source to drain path coupling VDD to the output of the band gap reference, and having a gate coupled to the output of the opamp. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A band gap reference comprising:
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an operational amplifier (opamp) having a (+) input, a (-) input, and an output, the opamp comprising; a first transistor (524) having a gate forming the (+) input of the opamp; a second transistor (525) having a gate forming the (-) input of the opamp, and a source to drain path connected on a first end to a first end of the source to drain path of the first transistor (524); and a current mirror comprising; a third transistor (521) having a source to drain path coupling VDD to a second end of the source to drain path of the first transistor (524), and having a gate; and a fourth transistor (522) having a source to drain path coupling VDD to a second end of the source to drain path of the second transistor (525), and having a gate coupled to the gate of the third transistor (521); a first resistor (Rn) having a first terminal coupled to VSS and a second terminal coupled to the first end of the source to drain path of the first transistor (524); a fifth transistor (528) having a source to drain path with a first end coupled to the second terminal of the first resistor (Rn), a second terminal, and having a gate coupled to the (+) input of the opamp; a first bipolar transistor (511) having an emitter to collector path coupling the (+) input of the opamp to VSS, and a base coupled to the second end of the source to drain path of the fifth transistor (528); a first current source transistor (501) having a source to drain path coupling VDD to the (+) input of the opamp, and having a gate coupled to the output of the opamp; a second resistor (R1) having a first terminal coupled to the (-) input of the opamp, and a second terminal; a second bipolar transistor (512) having an emitter to collector path coupling the second terminal of the second resistor (R1) to VSS, and a base coupled to the base of the first bipolar transistor (511); a second current source transistor (502) having a source to drain path coupling VDD to the (-) input of the opamp, and having a gate coupled to the output of the opamp; a third resistor (R2) having a first terminal forming the output of the band gap reference, and a second terminal; a third bipolar transistor (513) having an emitter to collector path coupling the second terminal of the third resistor (R2) to VSS, and having a base coupled to VSS ; and a third current source transistor (503) having a source to drain path coupling VDD to the output of the band gap reference, and having a gate coupled to the output of the opamp. - View Dependent Claims (15, 16, 17)
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Specification