JPH03154519A - Bipolar d/a converter - Google Patents

Abstract

PURPOSE:To prevent an offset error from fluctuating due to the changeover of the polarity by adding outputs of 2 sets of D/A converters applying DA conversion to a data stored in 2 registers in different polarity, and outputting the result. CONSTITUTION:A data written in registers 2, 3 is cleared when an H logic is issued to a clear terminal CL and a data is fetched when a write signal WR is supplied while an L logic is issued to the clear terminal CL. The data A is fetched in the register 2 when a write command signal WR is supplied while the polarity discrimination circuit SG is at an L logic state, the content of the register 3 is subject to polarity inversion by an inverter 13 and cleared to zero. Thus, one of the registers 2, 3 is cleared to zero without fail and a data corresponding to the analog voltage outputted to the other is written. The data written in the registers 2, 3 is DA-converted by D/A converters 4, 5 and the outputs of DA conversion are inputted to an analog adder 12 and they are added. Thus, even when the polarity changes, the offset voltage does not fluctuate.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a bipolar DA converter that outputs analog voltages of both positive and negative polarities.

"Conventional technology" FIG. 6 shows the configuration of a conventional bipolar DA converter.

A conventional bipolar DA converter has two registers 2 and 3 that temporarily store digital signals sent through a data bus line, and performs DA conversion on the digital data taken into these two registers 2 and 3, respectively. two D's
A converters 4 and 5, two switches 6 and 7 that select and extract analog voltages output by these two DA converters 4 and 5, and polarity determination included in digital data between these two switches 6 and 7. A switch control circuit 8 that selects and turns on one of the signals according to the hit signal, a buffer amplifier 9 that amplifies the analog signal taken out by the two switches 6 and 7, and an output from the buffer amplifier 9. The polarity inverting amplifier 11 amplifies an analog voltage signal to a predetermined level.

A write command signal WR is applied to registers 2 and 3 in synchronization with the supply of digital data, and the digital data to be DA-converted is loaded. Therefore, the same digital data is always written in the two registers 2 and 3, these two same data are input to the DA converters 4 and 5, and the respective DA converters 4 and 5 convert them into analog voltages with different polarities. Convert.

In the example shown in the figure, the DA converter 4 outputs O~+x m, and the DA
A case is shown in which the converter 5 is a DA converter that outputs -x (V) to 0 (v).

The data bus line 1 includes l bits of a polarity signal SG representing the polarity of data to be DA converted, and two switches 6 and 7 are selected by J (and L) of this polarity signal SG, so that one of the switches is When turned on, the polarity inverting amplifier 11 inverts the polarity of an analog voltage having a desired polarity and outputs the analog voltage.

"Problem to be Solved by the Invention" According to the bipolar DA converter having the circuit configuration shown in FIG. 6, the positive analog output and the negative analog output are output from the two DA converters 4 and 5, respectively. Therefore, if the offset error of these two DA converters is not O, ΔE is The offset error of the DA converter 4, -ΔE2, indicates the offset error of the DA converter 5.

This offset error is difficult to correct because it has different magnitudes. Another disadvantage is that the offset error causes discontinuity in the signal at the zero point.

Further, when the switches 6 and 7 are switched, spike noise is generated, and this spike noise causes a disadvantage that a circuit using an analog voltage at a subsequent stage malfunctions.

A first object of the present invention is to provide a bipolar DA converter in which the offset error does not change due to polarity switching.

A second object of the present invention is to provide a bipolar DA converter that does not generate spike noise even when polarity is switched.

"Means for Solving the Problem" In this invention, there are two registers, one of which takes in data depending on the polarity of the data to be DA-converted, and DA-conversion of the data stored in the two registers with different polarities. A bipolar DA converter is constructed by two DA converters that perform the following steps, and an analog adder that adds and outputs the DA conversion outputs of the two DA converters.

According to the configuration of the present invention, data to be DA-converted is written to the register corresponding to the polarity to be output, and zero is written to the other register. Data written to the two registers is always subjected to two DA-conversions. DA with different polarity on each device.
The converted outputs of the two DA converters are added by an analog adder and output.

Therefore, according to the bipolar DA converter of the present invention, two D
The outputs of the A converters are constantly added by an analog adder, and the polarity of the analog voltage to be output is switched depending on the presence or absence of data in the two registers.

As described above, since the present invention does not use a polarity changeover switch, no spike noise is generated when changing the polarity.

Furthermore, since the outputs of the two ODA converters are always added together by the analog adder, the offset errors ΔE1 and -ΔE2 are always added to a state of ΔE1 + (-ΔEx), which is maintained at a small value. Furthermore, even if the polarity of the analog voltage is switched, the offset error does not change.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a data bus line, 2 and 3 are registers, 4 and 5 are two DA converters that output analog voltages with different polarities, and 12
indicates an analog adder.

In this invention, two registers 2 and 3 are connected to the clear terminal CL.
A polarity determination signal SG is applied to the clear terminals CL of these two registers 2 and 3. The polarity determination signal SG is sent to the inverter 13 for one register 3.
The polarity is inverted and given by .

When H logic is applied to the clear terminal CL of registers 2 and 3, the written data is cleared and the clear terminal C
When a write signal WR is applied with L logic being applied to L, data is taken in. Therefore, as shown in FIG. 2, when the write command signal WR is applied with the polarity determination signal S G ;'l<L logic, the register 2 takes in data 8 and the contents of the register 3 are cleared to zero. Ru.

When the polarity determination signal SG is inverted to I (logic), the contents of the register 2 are cleared to zero, and when the write signal WR is applied at this time, the register 3 takes in the data B.

In this way, one of registers 2 and 3 is always cleared to zero, and data corresponding to the analog voltage to be output is written into the other.

The data written in registers 2 and 3 is DA-converted by DA converters 4 and 5, and the DA-converted outputs are input to analog adder 12 and added.

In this example, the analog adder 12 is constructed from a current adding circuit. That is, the outputs of the DA converters 4 and 5 are inputted to the virtual ground point of the operational amplifier 12A through the resistors R1 and R2, and the currents are added together at this virtual ground point.

"Effect of the invention" Figure 3 shows the output voltage Vi1 of the DA converter 4, and Figure 4 shows the DA converter 4 output voltage Vi1.
Output voltage Vi2 of converter 5, FIG. 5 shows analog adder 1
2 output voltage V. shows the output characteristics of each person.

As is clear from FIGS. 3 to 5, there is an offset error Δ in the output voltages VII and Viz of the two DA converters 4 and 5.
Even if El and -ΔE2 exist, the output voltage of the analog adder 12 ■. The offset error ΔEo included in is ΔEo−ΔE,+(−8E2), which is a small value. Here, if 1ΔE−1ΔEz l, ΔEo−
It becomes 0.

Furthermore, since the offset error is always calculated, there is no fluctuation in the offset voltage even if the polarity changes.

Therefore, there is no discontinuity in voltage changes from positive to negative and from negative to positive.

Furthermore, since a polarity changeover switch is not used, spike noise is not generated when changing the polarity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the invention, FIG. 2 is a waveform diagram for explaining the invention in detail, and FIGS. 3 to 5 are graphs for explaining the invention in detail. 6th
The figure is a block diagram for explaining the conventional technology, and FIG. 7 is a graph for explaining the operation of the conventional bipolar DA converter. 1; Data bus line, 2.3: Register, 45: DA
Converter, 12: Analog adder. book 1 diagram

Claims (1)

[Claims] (1) A: two registers that take data into one of them depending on the polarity of the data to be DA-converted, and B: two DA conversions that DA-convert the data stored in the above two registers with different polarities. A bipolar DA converter configured by C, an analog adder that adds and outputs the DA conversion outputs of these two DA converters.