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Analog to Digital Converter

IP.com Disclosure Number: IPCOM000097566D
Original Publication Date: 1961-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Lettieri, J: AUTHOR

Abstract

Rapid conversion of analog signals to digital form is effected by a solid state circuit which includes tunnel diodes D1... D7. The circuit operates on feedback and relative biasing principles. Transistors Q1... Q7 represent individual current sources which are associated with the significant binary digital positions of the output number from high order to low order, that is, X2/6/... X2/0/. The transistors Q1... Q7 are controlled by the status of operational amplifier transistors Q8.... Q14. The outputs of Q1... Q7, in turn, control sense amplifiers Q15... Q21, which furnish the final digital output at the lower set of terminals X2/6/... X2/0/. The respective outputs of Q15...Q20 are also fed back on lines 1...6 to a series of voltage divider networks which are respectively associated with the amplifiers Q9... Q14.

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Analog to Digital Converter

Rapid conversion of analog signals to digital form is effected by a solid state circuit which includes tunnel diodes D1... D7. The circuit operates on feedback and relative biasing principles. Transistors Q1... Q7 represent individual current sources which are associated with the significant binary digital positions of the output number from high order to low order, that is, X2/6/... X2/0/. The transistors Q1... Q7 are controlled by the status of operational amplifier transistors Q8.... Q14. The outputs of Q1... Q7, in turn, control sense amplifiers Q15... Q21, which furnish the final digital output at the lower set of terminals X2/6/... X2/0/. The respective outputs of Q15...Q20 are also fed back on lines
1...6 to a series of voltage divider networks which are respectively associated with the amplifiers Q9... Q14. The voltage divider networks range in size from a single feedback resistor which is connected to the base of Q9, to six feedback resistors which are connected to the base of Q14. The bias conditions of the operational amplifiers depend on a -12. 0 volt source, terminal 7. This is applied to each of the amplifiers as well as the feedback voltages from Q15... Q20. D8... D14 are Zener diodes which establish precise reference voltages at the collectors of the sense amplifiers for feedback purposes.

The resistors 64R(E)... R(E) establish predetermined currents through tunnel diodes D1... D7 so that each diode switches on at a different predetermined binary proportioned voltage level. Analog signals are applied at input terminal 8. If it is assumed that the initial input at the terminal 8 is zero, sources Q1... Q7, diodes D1... D7, the amplifiers Q8...Q14, and the amplifiers Q15... Q21 are in their off, or unsaturated, condition.

The EI characteristic for diodes D1... D7 is shown in the lower drawing. Any diode, when off, is at the no-current level I(0) (point A) on the curve and its associated sense amplifier off. Any diode, when on, passes a peak current I(P) (point B) which causes its associated sense amplifier to switch on.

In the circuit, when the input voltage from terminal 8 is +R(E)I(P), the...