# US 2010/0164467 A1 · Reference voltage generation circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2010/0164467 A1 - Document ID: US20100164467A1 - Status: Published application - Kind: A1 - Application number: 12/648,870 - Filed: 2009-12-29 - Published: 2010-07-01 - Earliest claimed: 2008-12-29 - Inventors: Eun-Sang Jo - Web page: https://patentgrep.com/patent/US20100164467A1 ## CPC - G05F 3/30: Regulators using the difference between the base-emitter voltages of two bipolar transistors operating at different current densities (G05F3/26 takes precedence) - G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES ## Abstract A reference voltage generation circuit includes an operational amplifier for outputting a constant voltage in accordance with reference voltages respectively input to an inverting terminal of the operational amplifier and a non-inverting terminal of the operational amplifier, and a start-up circuit for waking up the operational amplifier when the start-up circuit is switched from an idle mode to an active mode. The start-up circuit includes a first-type transistor having a gate connected to an output of the operational amplifier, a source connected to a supply voltage, and a drain connected to resistors, to supply a constant reference current to the resistors in accordance with an output voltage from the operational amplifier, thereby generating a band-gap output voltage. The resistors are connected in parallel to a stage, from which the band-gap output voltage is output, in order to generate a band-gap output voltage of about 0.6V. ## Claims ### Claim 1 An apparatus comprising: an operational amplifier for outputting a constant voltage in accordance with reference voltages respectively input to an inverting terminal of the operational amplifier and a non-inverting terminal of the operational amplifier; and a start-up circuit for waking up the operational amplifier when the start-up circuit is switched from an idle mode to an active mode, the start-up circuit comprising a first first-type transistor having a gate connected to an output of the operational amplifier, a source connected to a supply voltage, and a drain connected to first and second resistors, to supply a constant reference current to the first and second resistors in accordance with an output voltage from the operational amplifier, thereby generating a band-gap output voltage, wherein the first and second resistors are connected in parallel to a stage from which the band-gap output voltage is output. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the start-up circuit includes: a low pass filter comprising a second first-type transistor and a first second-type transistor, to remove radio-frequency noise from the band-gap output voltage; and a second second-type transistor for controlling the band-gap output voltage to be 0V in the idle mode. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the second first-type transistor of the low pass filter has a gate, and a source connected between the first and second resistors while being connected to the gate of the second first-type transistor. ### Claim 4 (depends on 2) The apparatus of claim 2, wherein the second first-type transistor of the low pass filter has a drain connected to a gate of the first second-type transistor. ### Claim 5 (depends on 2) The apparatus of claim 2, wherein the first second-type transistor has a source connected to a ground voltage, and a drain connected to the ground voltage. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the start-up circuit further includes: a second first-type transistor having a source connected to the supply voltage, a gate, and a drain connected to the gate of the second first-type transistor, the second first-type transistor being turned on when the start-up circuit is switched from the idle mode to the active mode; a first second-type transistor having a drain connected to the drain of the second first-type transistor, the first second-type transistor being turned off when the start-up circuit is switched from the idle mode to the active mode, thereby causing the supply voltage to be charged, as a drain voltage, in the drain of the first second-type transistor; a second second-type transistor having a gate connected to the drain of the second first-type transistor and the drain of the first second-type transistor, and a drain connected to the output of the operational amplifier, the second second-type transistor being turned on by the voltage charged in the drain of the first second-type transistor; and third and fourth second-type transistors each having a gate connected to a stage supplying an inverted power-down signal generated when the start-up circuit is switched from the idle mode to the active mode, the third and fourth second-type transistors being simultaneously turned on by the inverted power-down signal. ### Claim 7 (depends on 6) The apparatus of claim 6, wherein the first second-type transistor has a gate connected to the drain of the first first-type transistor, and a source connected to a drain of the fourth second-type transistor. ### Claim 8 (depends on 6) The apparatus of claim 6, wherein the second second-type transistor has a source connected to a drain of the third second-type transistor. ### Claim 9 (depends on 6) The apparatus of claim 6, wherein each of the third and fourth second-type transistors has a source connected to a ground voltage. ### Claim 10 (depends on 6) The apparatus of claim 6, wherein the third and fourth second-type transistors are turned off by the inverted power-down signal in the idle mode, and the first second-type transistor is turned off by a band-gap output voltage of about 0V generated in the idle mode. ### Claim 11 (depends on 1) The apparatus of claim 1, comprising: second and third first-type transistors each having a source connected to the supply voltage, each of the second and third first-type transistors outputting a bias current corresponding to the output voltage from the operational amplifier, using the supply voltage; a reference voltage circuit comprising first and second nodes respectively connected to the inverting and non-inverting terminals of the operational amplifier, to supply the reference voltages to the inverting and non-inverting terminals of the operational amplifier via the first and second nodes, using the bias currents output from the second and third first-type transistors, respectively; and a fourth first-type transistor having a source connected to the supply voltage, a gate connected to a stage supplying an inverted power-down signal, the fourth first-type transistor supplying the supply voltage to the second and third first-type transistors in accordance with the inverted power-down signal. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein: each of the second and third first-type transistors has a gate connected to the output of the operational amplifier; the second first-type transistor has a drain connected to the first node of the reference voltage circuit; and the third first-type transistor has a drain connected to the second node of the reference voltage circuit. ### Claim 13 (depends on 11) The apparatus of claim 11, wherein the fourth first-type transistor has a drain connected to the gates of the second and third first-type transistors. ### Claim 14 (depends on 11) The apparatus of claim 11, wherein the reference voltage circuit includes: a third resistor and a first bipolar transistor which are connected in parallel to the first node and the ground voltage; a fourth resistor and a second bipolar transistor which are connected in parallel to the second node and the ground voltage; and a fifth resistor connected in series between the second node and the second bipolar transistor. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein: the third resistor is connected to the second first-type transistor in series, and the fifth resistor is connected to the third first-type transistor in series while being connected to the fourth resistor in parallel; the first and second bipolar transistors have bases connected to the ground voltage, to constitute a current mirror; the first bipolar transistor has an emitter connected to the first node, and a collector connected to the ground voltage; and the second bipolar transistor has an emitter connected to the fifth resistor, and a collector connected to the ground voltage. ### Claim 16 (depends on 11) The apparatus of claim 11, wherein the fourth first-type transistor is turned on in the idle mode, and the output of the operational amplifier is charged with the supply voltage as the fourth first-type transistor is turned on, so that the second and third first-type transistors are turned off. ### Claim 17 (depends on 1) The apparatus of claim 1, wherein the first first-type transistor supplies a constant reference current to the first and second resistors, to generate a band-gap output voltage of about 0.6V. ### Claim 18 (depends on 1) The apparatus of claims 1, wherein the first-type transistors are P-channel type MOS transistors, and the second-type transistors are N-channel type MOS transistors. ### Claim 19 A method comprising: outputting a constant voltage from an operational amplifier in accordance with reference voltages respectively input to an inverting terminal of the operational amplifier and a non-inverting terminal of the operational amplifier; and waking up the operational amplifier with a start-up circuit when the start-up circuit is switched from an idle mode to an active mode, the start-up circuit comprising a first first-type transistor having a gate connected to an output of the operational amplifier, a source connected to a supply voltage, and a drain connected to first and second resistors, to supply a constant reference current to the first and second resistors in accordance with an output voltage from the operational amplifier, thereby generating a band-gap output voltage, wherein the first and second resistors are connected in parallel to a stage from which the band-gap output voltage is output. ### Claim 20 (depends on 19) The method of claim 19, wherein the start-up circuit includes: a low pass filter comprising a second first-type transistor and a first second-type transistor, to remove radio-frequency noise from the band-gap output voltage; and a second second-type transistor for controlling the band-gap output voltage to be 0V in the idle mode.