Amplifiers – With semiconductor amplifying device – Including differential amplifier
Reexamination Certificate
2008-03-11
2008-03-11
Nelms, David (Department: 2871)
Amplifiers
With semiconductor amplifying device
Including differential amplifier
C330S260000, C330S261000, C327S561000
Reexamination Certificate
active
11401492
ABSTRACT:
A folded-cascode operational amplifier including a differential input stage (19) and a class AB output stage (20) includes a first slew boost current mirror (13) and a second slew boost current mirror (14) having inputs connected to drains of the input transistors, respectively. Each current mirror amplifies excess tail current steered into it as a result of a large, rapid input signal transition. The amplified excess tail current is used to boost the slew rate of the class AB output stage in accordance with a first polarity of the difference between the first (Vin+) and second (Vin−) input voltages. The drains of the input transistors are maintained at a voltage less than a transistor threshold voltage above the ground except during slewing operation of the operational amplifier to effectively isolate the current mirrors except during slewing operation.
REFERENCES:
patent: 5446412 (1995-08-01), Kimyacioglu et al.
Brady III Wade James
Chung David
Nelms David
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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