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Double Emitter Suppressed Carrier Modulator

IP.com Disclosure Number: IPCOM000093127D
Original Publication Date: 1967-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Haist, CF: AUTHOR [+2]

Abstract

Double-emitter chopping transistor 10 has its emitter leads 11 and 12 connected as a bridge with identical resistors 13 and 14. Secondary 15 of a transformer is connected across the bridge in series with base 16 of transistor 10. Primary 17 of the transformer is connected to the carrier signal source e(c). Collector 18 of transistor 10 is connected to the mid-point of a pair of matched resistors 19 and 20. The latter form a second bridge with emitters 11 and 12 of transistor 10. A modulation signal source 21 applies a signal em through resistor 22 across the bridge. Anode 23 is connected across resistors 19 and 20.

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Double Emitter Suppressed Carrier Modulator

Double-emitter chopping transistor 10 has its emitter leads 11 and 12 connected as a bridge with identical resistors 13 and 14. Secondary 15 of a transformer is connected across the bridge in series with base 16 of transistor
10. Primary 17 of the transformer is connected to the carrier signal source e(c). Collector 18 of transistor 10 is connected to the mid-point of a pair of matched resistors 19 and 20. The latter form a second bridge with emitters 11 and 12 of transistor 10. A modulation signal source 21 applies a signal em through resistor 22 across the bridge. Anode 23 is connected across resistors 19 and 20.

By tying collector 18 of transistor 10 to a resistor bridge, and base 16 to a separate resistor bridge, any voltages developed by the circuits are balanced with respect to load impedance 23 and ground. The voltage developed across emitter 11 of transistor 10 to the base junction is equal and opposite to the voltage developed across emitter 12 to its base junction. Therefore, the sum of these voltages is approximately zero with respect to load impedance 23. Any stray capacitance between collector 18 and either emitter, or the base and either emitter, is also in the balanced RC bridge network.

The values of the bridge resistors and the collector bridge resistors are partially determined by the capacitance between both emitter junctions and the base and both emitter junctions and the collector. Because of the in...