The wipers of the switches associated with the magnitude digits of the number to be converted are connected to an R-2R resistance ladder network. The output of the resistance ladder network is connected as an input to a differential amplifier capable of operating in an inverting or non-inverting mode. The other input of the differential amplifier is resistively coupled to the wiper of the switch associated with the sign digit of the number to be converted whereby the output of the differential amplifier provides an analog signal of polarity and magnitude representative of the signed binary number to be converted.
United States Patent Kallio 14 1 May 7, Primary Examinerlhomas A. Robinson Attorney, Agent, or Firml-loward P. Terry; Samuel C. Yeaton ABSTRACT A digital-to-analog converter for transforming signed binary numbers to analog form comprises a plurality of single pole-double throw switches having first contacts commonly connected to a source of reference potential and second contacts commonly connected to ground potential.
The other input of the differential amplifier is resistively coupled to the wiper of the switch associated with the sign digit of the number to be converted whereby the output of the differential amplifier provides an analog signal of polarity and magnitude representative of the signed binary number to be' converted. Field of the Invention The invention pertains to digital-to-analog converters particularly of the type for converting signed digital numbers to bipolar analog signals.
Description of the Prior Art Digital-to-analog converters are well known in the prior art where the digits of the number to be converted control a plurality of single pole-double throw switches, respectively, for selectively connecting reference potentials to a ladder network whose output provides the corresponding analog signal. A type of ladder network commonly utilized in such converters is the well known R-2R resistance ladder network which is conveniently commercially procurable in modular form from numerous manufacturers of electronic circuit components.
The plurality of switches utilized in such converters are normally instrumented by solid state switching devices also commercially procurable in modular form as ladder switch modules from manufacturers of electronic circuit components.
Such ladder switch modules are normally provided with one contact of each of the switches connected to a common bus terminating at an input connector to the module.
The other contact of the switches are normally commonly connected to another bus which terminates at another input connector to the module. Such switch modules normally provide input terminals to control the positioning of the switches, respectively, and output terminals associated with the wipers of the respective switches are also normally provided.
It is therefore appreciated thata convenient presentday method for constructing digital-to-analog converters is to procure an appropriate resistance ladder network module and an appropriate ladder switch module interconnecting the two to form the converter.
It is normally desirable in present-day data handling or control systems to convert signed digital numbers to corresponding bipolar analog signals. One prior art configuration for instrumenting such bipolar converters is to utilize a matched pair of precision power supplies providing positive and negative reference potentials and connected to the two contact buses of the ladder switch module respectively. The precision reference power supplies of such converters represent a substantial portion of the cost thereof.
Therefore, in bipolar converters the necessity of having two such expensive power supplies unduly increases the cost of such converters. Additionally, the two required power supplies unduly increase the bulk and weight of the converter which may impose severe design limitations in, for example, airborne environments.
It is further appreciated that the precision power supplies are extremely difficult to design for proper operation over the wide temperature ranges often encountered in numerous converter environments. Another prior art bipolar digital-to-analog converter configuration involves grounding one of the contact buses of the ladder switch module and connecting the other contact bus through a separate single pole-double throw switch to the two precision reference power supplies; the separate switch being controllec by the sign digit of the number to be converted.
This arrange ment not only suffers from the disadvantage of requiring two precision power supplies, as previously discussed, but additionally requires a separate switch with contacts connected to the two supplies, respectively. This arrangement precludes using one of the switches of the ladder switch module for this purpose because of the common busing of vthe switch contacts thereof as previously discussed.
Another prior art bipolar digital-to-analog converter arrangement involves connecting the output of the ladder network to a differential output device with the differential outputs thereof connected to the contacts of a separate single pole-double throw switch, the switch being controlled by the sign digit of the number to be converted.
This arrangement hasthe disadvantage of requiring an additional switch since the switches of the ladder switch module cannot be used for this purpose for the reasons discussed above.
Additionally, the differential output device required in this arrangement is subject to differential unbalance which decreases the efficacious operation of the converter. Additionally, the polarity of the output is determined by a single pole-double throw switch controlled by the sign digit of the number to be converted where the contacts thereof are connected to the contact buses of the ladder switch module, respectively, thus permitting this switch to be included therein.
The converter comprises a plurality of single poledouble throw switches, the contacts thereof being connected to two contact buses respectively. A precision power supply is connected to one of the buses and the other bus is connected to ground potential.
The digits of the number to be converted are utiliized, respectively, to control the positioning of the switches. The switches associated with the magnitude digits of the number are connected to an impedance ladder network, the output of which being connected as an input to an inverting circuit. The other input to the inverting circuit is resistively coupled to the switch associated with the sign digit of the number to be converted. Thus, the output of the inverting circuit provides an analog signal of polarity and magnitude representative of the signed digital number to be converted.
I is a schematic wiring diagram ofa bipolar digital-to-analog converter configured in accordance with the invention; and. The converter 10 includes a register 11 for holding the signed binary number to be converted.
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Resident Evil review. What your name means in Urban Dictionary. Windows Windows. Most Popular. New Releases. Desktop Enhancements. It is an object of the invention to provide a digital to analog converter which is not increased in its manufacturing cost, even if the characteristic of eliminating an error in analog signals is added thereto.
According to the invention, a digital to analog converter comprises,. The invention will be explained in more detail in accordance with following drawings wherein,. Before describing a digital to analog converter according to the invention, a conventional digital to analog converter as briefly described before will be described in FIG. The first analog signal and attenuated second signal are added in the adder 14 to produce the analog signal at the output terminal According to the conventional digital to analog converter, however, there is occured a remarkable error in the vicinity of the origin 0 of the coordinate axes, that is, a digital input "" binary as shown in FIGS.
In FIG. On the other hand, the errors are produced in FIG. If such very small digital signals as being -1, 0 and 1 like audio signals the center of which is positioned at the origin 0 are applied to the input terminals A0 to A7, analog signals of -2, 0 and 1 are produced at the output terminal 01 in FIG. Next, there is shown a digital to analog converter in a first embodiment according to the invention in FIG.
In the half adder 25, on the other hand, the control signal "high" is applied to one of the inputs of the NAND circuit N from a control terminal H1. The first decoder 27 is connected to the respective exclusive OR circuits EO of the half adders 21 to 24 and to the inverter I of the half adder 21, while the second decoder 28 is connected to the exclusive OR circuit of the half adder 25 and to input terminals A0 to A2.
The common connecting point of the transistors 37 is connected to the adder 34 having an output terminal The common connecting point of the transistors 38 is connected to the input of the attenuator 31 which is connected to the adder 34 at the output thereof. In operation, when such an eight bit digital signal as including "high" and "low" bits is applied to the input terminals A0 to A7, upper five bits thereof are received in the half adders 21 to 25, and lower three bits thereof are received at the lower three inputs of the second decoder In the half adder 25, the following addition is performed.
As clearly understood from the above table, a carry signal which is the output of the inverter I is produced, when a bit of the input terminal A3 is "high" so that a signal "high" is applied to the exclusive OR circuit EO and NAND circuit N in the following half adder 24 whereby the same addition as mentioned above is performed therein. Such adding operations are repeated in the half adder 24 to In the first decoder 27, none of the output terminals is selected, when the output of the inverter I is "high" in the half adder Finally, the first analog signal and second analog signal thus attenuated are added to produce an analog signal at the output terminal As described above, the fixed value "" is added to the digital data applied to the input terminals A0 to A3 so that the origin 0 of the coordinate axes X and Y is shifted to the origin 0' as shown in FIGS.
As clearly shown in FIGS. Further, when the input digital signal is -1, that is, "", the added digital signal becomes "". In operation, when an input signal applied to the input terminals B4 to B8 is, for instance, "", an analog signal 2I is produced at the output terminal C because the transistor 45 5 is turned on by the output of the OR circuit
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