Operational amplifier with class-AB+B output stage
AssigneeNational Semiconductor Corporation
InventorAlexander Petrus Gerardus Lubbers
Life of this patent
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Abstract
An amplifier comprising: 1) a class-AB push-pull stage comprising a first P-channel output transistor and a first N-channel output transistor for driving an output load; and 2) a class-B current booster stage coupled in parallel with the class-AB push-pull stage comprising a second P-channel output transistor and a second N-channel output transistor for driving the output load. The small class-AB transistors have a minimum quiescent transconductance. The class-B current booster transistors are inactive in the quiescent state, but deliver large currents for output voltages approaching the power supply rails.
Claims20
An operational amplifier comprising:
- a class-AB push-pull stage comprising a first P-channel output transistor and a first N-channel output transistor for driving an output load;
- and
- a class-B current booster stage coupled in parallel with said class-AB push-pull stage comprising a second P-channel output transistor and a second N-channel output transistor for driving said output load.
A cellular telephone comprising:
- a radio-frequency (RF) transceiver for transmitting an outgoing RF signal and receiving an incoming RF signal;
- baseband processing circuitry for processing a forward channel baseband signal received from said RF transceiver and processing a reverse channel baseband signal sent to said RF transceiver;
- and
- an operational amplifier capable of amplifying at least one of an analog signal and a digital signal in said cellular telephone, said operational amplifier comprising:
- a class-AB push-pull stage comprising a first P-channel output transistor and a first N-channel output transistor for driving an output load;
- and
- a class-B current booster stage coupled in parallel with said class-AB push-pull stage comprising a second P-channel output transistor and a second N-channel output transistor for driving said output load.
An operational amplifier having an output stage comprising:
- a first P-channel transistor having a drain suitable for coupling to an output load and a source coupled to a VDD power supply;
- a second P-channel transistor having a drain suitable for coupling to said output load and a source coupled to said VDD power supply;
- a third P-channel transistor having a gate coupled to a gate of said first P-channel transistor and a source coupled to a gate of said second P-channel transistor;
- a first N-channel transistor having a drain suitable for coupling to said output load and a source coupled to ground;
- a second N-channel transistor having a drain suitable for coupling to said output load and a source coupled to ground;
- and
- a third N-channel transistor having a gate coupled to a gate of said first N-channel transistor and a source coupled to a gate of said second N-channel transistor.
Dependencies are inferred from the claim text.