Claims
- 1. A fixed voltage virtual ground generator circuit, comprising:
- a bias current source coupled to a first supply voltage;
- a bandgap voltage reference circuit having an output coupled to a voltage reference node and further coupled between said bias current source and a second supply voltage;
- an operational amplifier coupled to said voltage reference node in a unity gain configuration, having an output coupled to an output terminal, and powered by said bias current source and said second supply voltage;
- operable to provide a stable fixed voltage at the output terminal over a wide range of supply voltage and temperature conditions.
- 2. The virtual ground generator circuit of claim 1, wherein said bandgap voltage reference circuit further comprises:
- first and second resistors, coupled to said voltage reference node and further coupled to said second supply voltage, and further coupled to programmable fuses and resistances operable to enable programmation of said reference voltage to a precise, predetermined value.
- 3. The circuit of claim 1, wherein said bias current source further comprises transistors coupled for providing a reference current of a predetermined value, and further comprising transistors coupled as compensation circuitry, operable so that current variations with in the bias source due to ambient temperature variations do not change the reference current value.
- 4. The bias circuit of claim 3 wherein said compensation circuitry comprises JFET transistors.
- 5. The bias circuit of claim 3 wherein said compensation circuitry comprises isolated vertical bipolar transistors.
- 6. The circuit of claim 1, wherein said operational amplifier further comprises one differential input coupled to said reference voltage and a second differential input coupled to said voltage output.
- 7. The circuit of claim 1, wherein said operational amplifier further comprises an output stage coupled to said output terminal and further coupled to a boost stage, said boost stage operable to provide additional current sinking or sourcing capability when the current flowing through the output stage exceeds a predetermined threshold.
- 8. The operational amplifier of claim 7, wherein said output stage further comprises a sensing transistor coupled to said boost stage, and operable to turn on said boost stage when the current flowing through the conduction path of said sensing transistor exceeds a certain threshold.
- 9. The operational amplifier of claim 8, wherein said boost stage comprises a first and second bipolar transistor, each having its base coupled to said sensing transistor, and each having its conduction path coupled between said voltage output and one of said voltage supplies, operable to provide increased current flow through the conduction paths of said first or second transistor when the current flowing at the voltage output exceeds said predetermined threshold.
- 10. The operational amplifier of claim 7, wherein said output stage is coupled to a plurality of gain stages, coupled together and further coupled to said voltage reference node, operable to provide a large gain in signal amplitude from said voltage reference to said output stage.
- 11. The operational amplifier of claim 1, wherein said operational amplifier is comprised of isolated vertical bipolar transistors coupled to form a differential input stage, a plurality of gain stages coupled together and to the differential input stage, and an output stage coupled to said voltage output.
- 12. The circuit of claim 1, wherein said operational amplifier further comprises a plurality of resistors coupled with programmable fuses, operable to allow selective programmation of the offset voltage of said operational amplifier, to allow minimization said offset voltage.
- 13. A method for creating a virtual ground reference voltage for use in a single supply system, comprising the steps of:
- providing a bandgap voltage reference circuit coupled to a voltage reference node;
- providing a temperature stable bias current source coupled to said first voltage supply and to said bandgap voltage reference circuit;
- providing an operational amplifier having increased current drive capability, powered by said bias current source and said second voltage supply;
- coupling a said voltage reference node to a first input terminal of said operational amplifier;
- coupling the output of said operational amplifier to a voltage output terminal, and further coupling said voltage output terminal to a second input terminal of said operation amplifier; and
- operating said operational amplifier in a unity gain configuration so as to provide a voltage at the voltage output terminal that is equal to the fixed voltage provided by the bandgap voltage reference circuit over a wide range of supply voltages and temperature conditions.
- 14. The method of claim 13, and further comprising the step of providing a precision voltage resistor divider coupled to said bandgap reference generator in a parallel fashion, and having programmable fuses operable to disable said bandgap reference generator and enable said voltage divider.
- 15. The method of claim 13, wherein said step of providing an operational amplifier comprises providing an operational amplifier fabricated from isolated vertical bipolar transistors.
- 16. The method of claim 15, wherein said step of providing an operational amplifier further comprises providing an operational amplifier having a boost circuit comprising a first and second isolated vertical bipolar transistor each having their conduction paths coupled between said output voltage terminal and one of said first and second voltage supplies.
- 17. An integrated circuit implementing a virtual ground reference voltage circuit, comprising:
- first and second voltage supply terminals;
- a voltage output terminal;
- a bias current source coupled to said first supply voltage;
- a bandgap reference circuit, coupled to a voltage reference node and further coupled between said first and second supply voltages, operable such that a predetermined reference voltage is available at the voltage reference node;
- an operational amplifier coupled to said reference voltage node in a unity gain configuration, having an output coupled to said output terminal, and powered by said bias current source and said second supply voltage; and
- operable to provide a stable voltage at the output terminal which is equal to a predetermined value between said first and second supply voltages over a wide range of supply voltage and temperature conditions.
- 18. A fixed voltage generator circuit, comprising:
- a bias current source coupled to a first supply voltage;
- a bandgap reference circuit having an output coupled to a voltage reference node and further coupled to said bias current source and to a second supply voltage;
- an operational amplifier in a unity gain configuration coupled to said voltage reference node, having its output coupled to an output terminal;
- said operational amplifier having an output stage coupled to said output terminal and further coupled to a boost stage, said boost stage operable to provide additional current sinking or sourcing capability when the current flowing through the output stage exceeds a predetermined threshold; and
- operable to provide a stable fixed voltage at the output terminal.
- 19. The fixed voltage generator circuit of claim 18, wherein said fixed voltage at the output terminal is a voltage halfway between the first and second supply voltages.
- 20. The bandgap reference circuit of claim 18, wherein said bias current source comprises circuitry operable to provide a constant current of predetermined value over a range of temperature conditions.
- 21. The bandgap reference circuit of claim 20 wherein said bias current source further comprises transistors coupled as compensation circuitry operable such that current variations in the bias source due to ambient temperature variations do not change the constant current of predetermined value.
- 22. A fixed voltage generator circuit, comprising:
- a bias current source coupled to a first supply voltage;
- a differential amplifier in a unity gain configuration, coupled to a reference voltage, powered by said bias current source and having a voltage output;
- a bandgap reference generator circuit coupled between said bias current source and a second supply voltage source, and providing said reference voltage at its output; and
- operable to provide a stable fixed voltage at the output of the differential amplifier.
- 23. The fixed voltage generator of claim 22, wherein said output voltage is halfway between said first and second supply voltages.
- 24. The fixed voltage generator of claim 23, wherein said differential amplifier is an operational amplifier.
- 25. The fixed voltage generator of claim 23, wherein said bandgap reference generator circuit comprises a resistive voltage divider coupled to a bandgap reference circuit.
- 26. The fixed voltage generator of claim 25, wherein said resistive voltage divider comprises resistors whose values may be altered after said circuit is produced to reduce errors.
- 27. A method for producing a stable fixed voltage output circuit, comprising the steps of:
- providing a bias current source coupled to a first supply voltage;
- providing a differential amplifier in a unity gain configuration and powered by said bias current source and having a voltage output terminal;
- providing a voltage reference circuit coupled between said bias current source and a second supply voltage, and having an output; and
- coupling said voltage reference circuit to said differential amplifier and operating the circuit to produce a stable voltage at the voltage output terminal.
- 28. The method of claim 27, and further comprising the step of selecting the voltage reference at the output of said such that the voltage at the voltage output terminal is halfway between the first and second supply voltages.
- 29. A method for producing a stable fixed voltage output circuit, comprising the steps of:
- providing a bias current source coupled to a first supply voltage;
- providing a differential amplifier in a unity gain configuration and powered by said bias current source and having a voltage output terminal;
- providing a voltage reference circuit coupled between said bias current source and a second supply voltage, and having an output;
- coupling said voltage reference circuit to said differential amplifier and operating the circuit to produce a stable voltage at the voltage output terminal;
- wherein said step of providing a bias current source comprises selecting a bias current circuit which has a stable output which remains constant over a wide range of temperature and voltage conditions.
Parent Case Info
This application is a continuation of application Ser. No. 07/758,669, filed Sep. 12, 1991, now abandoned.
US Referenced Citations (25)
Continuations (1)
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Number |
Date |
Country |
Parent |
758669 |
Sep 1991 |
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