Browse Prior Art Database

Noise Isolation in Two-State Circuit

IP.com Disclosure Number: IPCOM000042666D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Spina, WJ: AUTHOR

Abstract

The circuit shown is a two-state circuit of bipolar transistors suitable to fix voltage levels and act as a buffer. As the normal high input voltage level on line 1 (5 volts) is the same as the highest operating voltage in the circuit, induced noise can reverse the relationship of the two output lines 3 and 5. This is prevented by diode 7 connected through resistor 9 to the 5-volt operating voltage, since diode 7 is back-biased at levels on line 1 higher than 5 volts. Transistor 11, with a constant 1-volt input to its base, operates through emitter-to-ground resistor 13 as a constant current source. Parallel transistors 15 and 17 supply this current from a 5-volt operating voltage acting through resistors 19 and 21 to the collectors of the respective transistors 15 and 17. A constant 2.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Noise Isolation in Two-State Circuit

The circuit shown is a two-state circuit of bipolar transistors suitable to fix voltage levels and act as a buffer. As the normal high input voltage level on line 1 (5 volts) is the same as the highest operating voltage in the circuit, induced noise can reverse the relationship of the two output lines 3 and 5. This is prevented by diode 7 connected through resistor 9 to the 5-volt operating voltage, since diode 7 is back-biased at levels on line 1 higher than 5 volts. Transistor 11, with a constant 1-volt input to its base, operates through emitter- to-ground resistor 13 as a constant current source. Parallel transistors 15 and 17 supply this current from a 5-volt operating voltage acting through resistors 19 and 21 to the collectors of the respective transistors 15 and 17. A constant 2.3-volt signal is applied on line 25 to the base of transistor 17 to serve as a comparison with the level on line 23 to the base of transistor 15. Line 23 is connected to the junction of diode 7 and resistor 9. The polarity of diode 7 is such as to pass current when line 1 is at a low level. The circuit provides two outputs, the one on left line 3 being denominated VOL and the one on right line 5 being denominated VOR. Where, on output, VOL or VOR is high, that level normally will be substantially 5 volts, and the other will be at a low level, typically 4.6 to 4.7 volts. This occurs because the higher voltage on lines 25 and 23 acts through the common connection of the emitters of transistors 15 and 17 to back-bias one of those transis...