Combination driver-summing circuit for rail-to-rail differential amplifier
AssigneeNorth American Philips Corporation
InventorsJohan H. Huijsing, John P. Tero
Life of this patent
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Abstract
A combination driver/summing circuit for rail-to-rail operation of a differential amplifier includes a differential amplifier input stage that amplifies an input signal and a current control circuit that regulates the operating currents through the active elements of the differential amplifier input stage. A summing circuit divided into first and second segments and supplied with current from a single common floating current source combines internal currents supplied by the differential amplifier input stage. A class A-B driver/output stage is coupled to the summing circuit to derive at least one output signal representative of the input signal and which is operative over nearly the full rail-to-rail supply voltage range.
Claims17
A differential amplifier with rail-to-rail common-mode range comprising:
- a positive supply voltage rail,
- a negative supply voltage rail,
- first and second amplifier input terminals for receiving a signal to be amplified,
- differential amplifier means comprising input means coupled to said first and second amplifier input terminals, output means, a first pair of transistors connected as a first differential amplifier to said positive supply voltage rail via a first current source, and a second pair of transistors connected as a second differential amplifier to said negative supply voltage rail via a second current source,
- a current summing circuit coupled to the output means of the differential amplifier means,
- a driver/output stage including first and second output transistors coupled to signal output terminal and having input means coupled to the current summing circuit, and
- a floating current source coupled to said summing circuit in a manner so as to control and to maintain a constant quiescent bias current in the output transistors.
A differential amplifier comprising:
- a positive supply voltage rail;
- a negative supply voltage rail,
- first and second amplifier input terminals for receiving a signal to be amplified,
- a rail-to-rail input stage comprising a first differential amplifier pair coupled to said positive supply voltage rail via a first current source, and a second complementary differential amplifier pair coupled to said negative supply voltage rail via a second current source,
- a current summing circuit,
- means coupling input means of the input stage to said first and second amplifier input terminals and output means of the input stage to the current summing circuit,
- a class AB biased driver/output stage including first and second complementary output transistors directly coupled to the current summing circuit and also coupled to signal output terminal of the differential amplifier, and
- a floating current source coupled to said summing circuit in a manner so as to control and to maintain a constant quiescent bias current in the output transistors whereby the quiescent bias current is independent of current conduction in the first and second differential amplifier pairs and of an input common-mode voltage.
Dependencies are inferred from the claim text.