Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1997-12-16
1999-08-17
Mottola, Steven J.
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330292, 330300, H03F 326, H03F 345
Patent
active
059399449
ABSTRACT:
A push-pull output stage includes an NPN pull-up transistor (Q6) and an NPN pull-down transistor (Q7) connected to an output. A compensation capacitor 17 is coupled between the collector and base of the pull-down transistor. A differential input stage includes emitter-coupled first (Q2) and second (Q3) NPN input transistors each coupled by a degeneration resistor to a constant current source. A base of the first NPN input transistor (Q2) is coupled to receive a shifted input voltage (V.sub.IN), and a base of the second NPN input transistor is coupled to the output conductor (3). The collectors of the first (Q2) and second (Q3) input transistors are connected to the sources of a folded cascode circuit including first (J1) and second (J2) cascode P-channel JFETs, respectively, the drains of which are connected to a current mirror output transistor (Q5) and a current mirror control transistor (Q4), respectively. The collector of the current mirror output transistor (Q5) is connected to the base of the pull-down transistor (Q7). The voltage gain of the output stage is determined primarily by the degeneration resistors and the compensation capacitor and hence is quite independent of the load impedance, and therefore provides stable circuit operation. A shoot-through current limiting circuit includes a capacitor and a resistor coupled between the input (V.sub.IN) and the base and collector of the current mirror control transistor (Q4).
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"Power Op Amps Sport Rail-to-Rail I/O Control Up To 3 A At 70 V" by Frank Goodenough, Electronic Design, May 1, 1997, two pages.
Burr-Brown Corporation
Mottola Steven J.
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