Apparatus for converting between digital and analog values

In combination for converting binary valves to analog values where the binary values are represented by first and second pluralities of binary signals respectively corresponding to rows and columns,

• a plurality of output means disposed in a matrix relationship defining rows and columns;
• first means for decoding the first plurality of signals to obtain signals for introduction to the different rows of output means to prepare an individual one of the rows for activation,
• second means for decoding the second plurality of signals to obtain signals for introduction to the different columns of output means to prepare an individual one of the columns for activation,
• third means for introducing the decoded signals in the first plurality to the inputs to the rows to prepare the output means in the individual one of the rows for activation,
• fourth means for introducing the decoded signals in the second plurality to the inputs to the columns to prepare the output means in the individual one of the columns for activation and to obtain an activation of a particular one of the output means common to the prepared row and column;
• and
• fifth means responsive to the activation of the particular output means for obtaining an activation of the output means in the rows preceding the particular output means in the prepared row and an activation of the output means in the rows preceding the prepared row, the output means including:
• first, second and third transistors,
• each of the first, second and third transistors having first, second and third elements,
• means responsive to the activation of the output means by the third, fourth and fifth means for introducing signals to the first elements in individual ones of the first transistors in accordance with such activation,
• means for biasing the first elements in the second transistors to a state of conductivity,
• means for biasing the first elements in the third transistors to obtain continuously a substantially constant flow of current through the third transistors,
• the second elements in the first and second transistors and the third element in the third transistor in each group having a common connection,
• the third elements in the first transistors receiving a reference voltage,
• means for applying an energizing voltage to the second elements in the third transistors to provide for the flow of the substantially constant current through each of the third transistors and through the conductive one of the first and second transistors associated with such third transistor, and
• means responsive to the cumulative currents on the third elements of the second transistors for providing an indication of the analog value,
• there being distributed capacitances across each of the first transistors, the distributed capacitances across each of the first transistors being charged during the state of non-conductivity in such first transistor and being operative during such charging to facilitate a state of conductivity in the associated one of the second transistors without any overshooting of the output voltage on the third terminal of such second transistor, the distributed capacitances across each of the first transistors being discharged upon the occurrence of a state of conductivity in such transistor to expedite the time that such first transistor passes the substantially constant current from the associated one of the third transistors and that the associated second transistor changes from a state of conductivity to a state of non-conductivity.

In combination,

• a first transistor having first, second and third elements,
• a second transistor having first, second and third elements,
• the third element of the first transistor and the first element of the second transistor being common,
• an operational amplifier,
• means for providing a first reference voltage,
• means for providing a second reference voltage and for introducing the second reference voltage to the second element of the second transistor,
• means for providing a reference potential,
• an operational amplifier responsive to the first and second reference voltages for producing a resultant voltage representative of the difference between the first and second reference voltages and for introducing the resultant voltage to the second element of the first transistor,
• means for applying an energizing voltage to the first element of the first transistor,
• means for providing a particular impedance between the first reference voltage and the reference potential,
• means for feeding the voltage on the third element of the second transistor back to the first reference voltage means, and
• means operatively coupled to the second elements of the first and second transistors for producing through the first and second transistors a flow of current regulated by the resultant voltage introduced to the first element of the second transistor.

In combination,

• a first transistor,
• a second transistor,
• an operational amplifier,
• means for introducing to the operational amplifier first and second reference voltages each having an opposite polarity for the other and each having at times a different magnitude than the other to obtain the production by the operational amplifier of a resultant voltage representing any difference between the magnitudes of the first and second reference voltages,
• means for providing a reference potential,
• an impedance connected to the first voltage reference means and the reference potential,
• means responsive to the resultant voltage from the operational amplifier for introducing the resultant voltage to the first transistor,
• means responsive to the voltage from the second transistor for introducing such voltage to the first reference voltage means to regulate the magnitude of the first reference voltage, and
• a plurality of current means each responsive to the first and second reference voltages for producing a substantially constant current in such current means.

In combination,

• first and second transistors connected in a series relationship,
• means for providing first and second reference voltages,
• an operational amplifier responsive to the first and second reference voltages for providing an output voltage dependent upon any difference between the first and second reference voltages,
• means connected to the first reference voltage means for producing a reference current,
• means including the first and second transistors for responding to the output voltage from the operational amplifier to produce a voltage for introduction to the first reference voltage means to regulate the current through the first and second transistors in accordance with the reference current, and
• at least one current cell means operatively coupled to the operational amplifier and the second reference voltage means for producing the regulated current through the current cell means.

In combination,

• first and second transistors connected in a series relationship,
• means including a first reference voltage for providing a reference current,
• an operational amplifier,
• means including the first reference voltage means and a second reference voltage means and the operational amplifier for introducing to the first transistor a voltage representative of the difference between the first and second reference voltages to obtain a current through the first and second transistors, and a voltage in the second transistor, in accordance with such voltage difference,
• means responsive to the voltage in the second transistor for introducing such voltage to the operational amplifier to regulate the current through the first and second transistors, and
• means including a current cell responsive to the difference voltage and the second reference voltage for producing the regulated current through the current cell.

In combination,

• means including a first reference voltage means for providing a regulated flow of current,
• means for providing a second reference voltage,
• means responsive to the first reference voltage and the second reference voltage for providing a voltage representative of the difference between the first and second reference voltages,
• control means responsive to the difference voltage for producing a flow of current and a feedback voltage dependent upon such flow of current,
• means responsive to the feedback voltage for providing for the regulation of the voltage difference to obtain the regulated current through the control means, and
• means including a current cell responsive to the voltage difference and the second reference voltage for producing the regulated current through the current cell.