Monolithically integrated output stage

Details Monolithically integrated output stage Monolithically integrated output stage

1998-08-28

2001-08-07

Zweizig, Jeffrey (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Current driver

C327S483000

Reexamination Certificate

active

06271694

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a monolithically integrated output stage.
BACKGROUND INFORMATION
Known monolithically integrated output stages are used to detect a load current threshold. whereby a switching signal is supplied by a switching logic unit over an output transistor on reaching a set load current threshold. Such output stages are used, for example, in electronic ignition control devices for motor vehicles.
German Published Patent Application No. 43 33 359 A1 describes such a monolithically integrated output stage. However, a disadvantage of the output stage described in German Published Patent Application No. 43 33 359 A1 is that the collector of the switching transistor of the output stage is pulled to an inverse voltage of <0 volt when inductive loads are switched, so that the output transistor of the switching logic can be notched up (i.e becomes unblocked). This occurs despite the fact that the threshold of the load current to be detected has not been reached. This leads to corruption of the signal.
To keep the output transistor blocked even when the collector voltage drops below 0 volt, German Patent Application No. 43 33 359 A1 proposes that a malfunction of the switching logic in inverse operation of the output stage be achieved over a potential-limiting diode and an additional transistor. The output transistor is wired here as a pull-down transistor, so that the interference signals can only be removed at a considerable expense.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a monolithically integrated output stage that avoids, in a simple manner that is advantageous over the known output stage discussed above, the malfunction of an output transistor in an inverse operation of the output stage. Because the emitter of the output transistor is connected to the logic output and a switching means is provided which blocks the output transistor in response to a negative collector voltage of the power switching transistor, a high interference immunity is achieved because the output transistor which is wired as a pull-Up transistor can be activated only by an active high signal which is in phase opposition to a low interference signal, and noise-free activation over a transistor is also achieved. The output transistor thus remains reliably blocked even in inverse operation of the output stage where the collector voltage drops below 0 volt, and it does not supply an output signal that signals a load current threshold value.


REFERENCES:
patent: 5539301 (1996-07-01), Uebele
patent: 43 33 359 (1995-01-01), None

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