Noise Isolation in Two-State Circuit
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
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.