Differential line driver
First Claim
1. A data network, comprising:
- (A) an unshielded transmission line;
(B) a pair of transceivers coupled together through the transmission line, each one of such transceivers comprising;
a differential line driver for feeding a differential logic output signal to the transmission line, such differential line driver comprising;
(i) a pair of transistors arranged as a differential pair for driving the transmission line with the differential logic output signal produced in accordance with an differential logic input signal fed to base electrodes of the pair of transistors; and
,(ii) circuitry for suppressing EMI emissions generated by common mode voltage switching transients produced at collector electrodes of the pair of transistors in response to changes in the differential logic input signal.
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Accused Products
Abstract
A differential line driver having a pair of transistors arranged as a differential pair for driving a transmission line with a differential logic output signal produced in accordance with a differential logic input signal fed to the base electrodes of the pair of transistors. The differential line driver includes circuitry for suppressing EMI emissions generated by common mode voltage switching transients produced at the collector electrodes of the pair of transistors in response to changes in the differential logic input signal. The common mode voltage switching transient suppression circuitry includes a pair of additional transistors. The differential logic input signal is fed to base electrodes of the additional transistors, and through such additional transistors, to the base electrodes of the pair of transistors of the differential pair. In one embodiment of the invention, the additional transistors are connected in a Darlington pair arrangement with the pair of transistors of the differential pair. While switching transients is the common mode voltage is still present because of the transient base current produced in the pair of transistors of the differential pair, the magnitude of the base current is attenuated by a factor β+1, where β is the beta of the additional (i.e., Darlington pair) of transistors. In another embodiment of the invention, the pair of transistors of the differential pair are NPN transistors and the additional, Darlington connected, pair of transistors are PNP transistors.
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Citations
20 Claims
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1. A data network, comprising:
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(A) an unshielded transmission line; (B) a pair of transceivers coupled together through the transmission line, each one of such transceivers comprising; a differential line driver for feeding a differential logic output signal to the transmission line, such differential line driver comprising; (i) a pair of transistors arranged as a differential pair for driving the transmission line with the differential logic output signal produced in accordance with an differential logic input signal fed to base electrodes of the pair of transistors; and
,(ii) circuitry for suppressing EMI emissions generated by common mode voltage switching transients produced at collector electrodes of the pair of transistors in response to changes in the differential logic input signal.
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2. A data network, comprising:
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(A) an unshielded transmission line; (B) a pair of transceivers coupled together through the transmission line, each one of such transceivers comprising; a differential line driver for feeding a differential logic output signal to the transmission line, such differential line driver comprising; (i) a pair of transistors arranged as a differential pair for driving the transmission line with the differential logic output signal produced in accordance with an differential logic input signal fed to base electrodes of the pair of transistors; and
,(ii) circuitry for suppressing EMI emissions generated by common mode voltage switching transients produced at collector electrodes of the pair of transistors in response to changes in the differential logic input signal; and wherein the EMI emission suppression circuitry includes; a pair of additional transistors; and wherein the differential logic input signal is fed to base electrodes of the additional transistors, and through such additional transistors, to the base electrodes of the pair of transistors of the differential pair. - View Dependent Claims (3, 4, 5, 6, 7, 8)
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9. A data network wherein a pair of transceivers are coupled together through a transmission line, each one of such transceivers including a differential line driver for feeding a differential logic output signal to the transmission line, such differential line driver comprising:
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a pair of transistors arranged as a differential pair for driving the transmission line with the differential logic output signal produced in accordance with an differential logic input signal fed to base electrodes of the pair of transistors; circuitry for suppressing common mode voltage switching transients produced at collector electrodes of the pair of transistors in response to changes in the differential logic input signal.
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10. A data network wherein a pair of transceivers are coupled together through a transmission line, each one of such transceivers including a differential line driver for feeding a differential logic output signal to the transmission line, such differential line driver comprising:
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a pair of transistors arranged as a differential pair for driving the transmission line with the differential logic output signal produced in accordance with an differential logic input signal fed to base electrodes of the pair of transistors; circuitry for suppressing common mode voltage switching transients produced at collector electrodes of the pair of transistors in response to changes in the differential logic input signal; and wherein the common mode voltage switching transient suppression circuitry includes; a pair of additional transistors; and wherein the differential logic input signal is fed to base electrodes of the additional transistors, and through such additional transistors, to the base electrodes of the pair of transistors of the differential pair. - View Dependent Claims (11, 12, 13)
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14. A differential line driver, comprising:
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a pair of transistors arranged as a differential pair for driving a transmission line with a differential logic output signal produced in accordance with a differential logic input signal fed to base electrodes of the pair of transistors; circuitry for suppressing common mode voltage switching transients produced at collector electrodes of the pair of transistors in response to changes in the differential logic input signal.
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15. A differential line driver, comprising:
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a pair of transistors arranged as a differential pair for driving a transmission line with a differential logic output signal produced in accordance with a differential logic input signal fed to base electrodes of the pair of transistors; circuitry for suppressing common mode voltage switching transients produced at collector electrodes of the pair of transistors in response to changes in the differential logic input signal; and wherein the common mode voltage switching transient suppression circuitry includes; a pair of additional transistors; and wherein the differential logic input signal is fed to base electrodes of the additional transistors, and through such additional transistors, to the base electrodes of the pair of transistors of the differential pair. - View Dependent Claims (16, 17, 18)
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19. A differential line driver, comprising:
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a first pair of bipolar transistors arranged as a differential pair; a second pair of bipolar transistors, one of the first and second pair of transistors being NPN transistors and the other one of the pair of transistors being PNP transistors; wherein base electrodes of the second pair of transistors are adapted for coupling to an input logic signal, emitter electrodes of the second pair of transistors being coupled to base electrodes of the first pair of transistors and collector electrodes of both transistors in the second pair of transistors being coupled to both emitters of the first pair of transistors. - View Dependent Claims (20)
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Specification