JPS60241307A - Multiplication type d-a converter - Google Patents

Abstract

PURPOSE:To operate a device for an analog input signal of either polarity by using two unipolar multiplication type D-A converters which have the same characteristics. CONSTITUTION:With respect to one D-A converter DAC1, a digital input signal Di is inputted to the digital input terminal, and the sum of an analog input signal Vi and a bias signal Vb is inputted to the analog input terminal. With respect to the other converter DAC2, the input signal Di is inputted to the digital input terminal, and only the bias signal Vb is inputted to the analog input terminal. An analog output signal {Di.Vb/R} of the converter DAC2 is subtracted from an analog output signal {Di(Vi+Vb)/R} of the converter DAC1, and the result is outputted. Thus, the device is operated for the analog input signal of either polarity.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a D-A conversion technique and a technique particularly effective when applied to a multiplication-type D-A converter that uses digital signals and analog signals as calculation inputs. So, even if it's 77,
The present invention relates to a technique effective for use in a four-quadrant multiplication type DA converter.

[Background technology]

Generally, a D-A converter has its conversion output level (gain)
It has a reference level input terminal for determining. Therefore,
When an analog signal is input to this reference level input terminal, an analog signal having a level corresponding to the product of this analog input signal and the digital input signal is obtained from the D-Ai conversion output terminal. It can be used as a so-called multiplication type D-A converter.

For example, in the Practical Electronic Circuit Handbook (pages 412497-252, published by CQ Publishing Co., Ltd. on November 30, 1979), there is a multiplication type D
-A converter is described. The one described in the same book uses a C-MOS type D-A converter,
It is configured as a so-called four-quadrant multiplication type D-A converter. This four-quadrant multiplication type D-A converter can be used regardless of whether its analog input signal has a positive or negative polarity, and its converted output signal can have either a positive or negative polarity.

However, the above-mentioned four-quadrant multiplication type D-A converter can only be configured with a bipolar C-MO8 type D-A converter that can operate with either positive or negative reference voltage. It cannot be configured with a unipolar DA converter that can only operate with either positive or negative polarity. For example, most bipolar type DA converters are unipolar and cannot constitute a four-quadrant multiplication type DA converter as described above.

On the other hand, bipolar D-A converters have many advantages over C-MOS types, such as current drive capability and operating speed. There is a demand for constructing a multiplication type D-A converter that can operate with analog input signals.

[Purpose of the invention]

The purpose of this invention is to provide a uni-polar D-A that can only operate with analog input signals of either positive or negative polarity.
A bipolar multiplier type D-A that can operate with analog input signals of either positive or negative polarity with a converter.
It provides conversion technology.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, using two unipolar D-A converters.
This means that even a unipolar D-A converter that can only operate with analog input signals of either positive or negative polarity can now operate with analog input signals of either positive or negative polarity. It accomplishes its purpose.

〔Example〕

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

In the drawings, the same reference numerals indicate the same or similar parts.

FIG. 1 shows a first embodiment of a multiplication type DA converter according to the present invention.

The multiplier type D-A converter shown in the same figure has a unipolar analog input terminal V r M that is effective only for either positive or negative polarity.
1, VrM2, two multiplying type D-A converters DAC having the same characteristics], DAC2, and the analog input terminals VrM1. A circuit for generating a bias signal (Vb) having a polarity on the effective side with respect to VrM2. Here, for one D-A converter DACIK, the digital input signal Di is input to its digital input terminal Dinl, and the analog input terminal V
The sum of the rM11C analog input signal (Vi) and the bias signal (Vb) is input. Also, the other D −
For the A converter DAC2, its digital input terminal D
The digital input signal Di is input to in2, and only the bias signal (vb) is input to the analog input terminal V r M2. And one D
−A converter DAC1 analog output signal N) i (V
i+Vb)/R) to the other 17) DA converter DA
It is characterized in that the analog output signal (Di-Vb/R) of C2 is subtracted and output.

Here, to describe the embodiment shown in FIG. 1 in more detail, the analog input signal (Vi) and the bias signal (vb) are both voltage signals having voltage values of Vi and vb.

The D-A converters DACI and DAC2 are each
Reference level input terminals VrM1 and VrLl and VrM2 and V for determining the conversion output level (gain)
It has rL2. One reference level input terminal VrM1. for determining the converted output level. These analog input terminals VrM1 .VrM2 are respectively used as said analog input terminals. VrM2 each functions as a current addition type input terminal. Furthermore, this D-A converter D
ACI and DAC2 are bipolar type D-A converters, and their analog input terminals VrM1. VrM2
operates effectively only for input voltages of positive polarity. In other words, the terminal VrM1. Current must always flow into the VrM2 side, and operation at full current cannot be achieved with opposite polarity, ie, negative input voltage.

Furthermore, the digital signal Di input to each digital input terminal Dinl and Din2 of the D-A converters DACI and DAC2 is an 8-bit binary encoded parallel "signal, and is expressed in hexadecimal notation from 00 to FF. Takes the value up to.

In the illustrated embodiment, this digital signal Di is input from a digital signal generating section O consisting of a clock pulse generating circuit 129, a cyclic counter 14, and a table memory 16. For example, a trigonometric function table is written in the table memory 16 using address data as an index. The address specification of this table memo IJ16 is cyclic counter 1.
This is done with the parallel count contents of 4. This cyclic counter 14 counts pulses of a constant period emitted from the clock pulse generation circuit 12, and when the count is up, starts counting again from the reset state, which is repeated periodically. Each time the count contents go around, the index of the function table is sequentially addressed from 0 degrees to 360 degrees. Then, the function values corresponding to the specified address positions are sequentially read out from the data output of the table memory 16, and
Each digital input terminal D in 1 of the D-A converter DACI, DAC2. D in 2 is given respectively. In other words, in this case, the sine wave digital signal D
i is applied to digital input terminals Dinl and Din2 of the D-A converters DAC1 and DAC2, respectively.

The bias voltage vb is applied to the two D-A converters DAC1 and DAC through a resistor R that determines an analog calculation coefficient.
2 each analog input terminal V i n 1 .

Each is input to Vin2. At this time, one D-
The analog input terminal VinlK of the A converter DAC is inputted with a current added to the analog input voltage Vi. Further, only the bias voltage vb is input to the analog input terminal Vin2 of the other D-A converter DAC2. Furthermore, this bias voltage vb is set to a voltage value such that the sum with the analog input voltage Vi is always positive. In other words, even if the negative polarity side pressure of the analog input voltage Vi is lost, the voltage is such that the negative polarity can be canceled and the analog input terminal V r M 1 of the DA converter DAd1 can always be made positive. is set to

The respective conversion outputs of the two DA converters DACI and DAC2 are subjected to analog subtraction operation from each other by operational amplifiers AI and A2 a). Then, the result of this subtraction is the multiplication type D−
It is designed to be derived as the analog conversion output Vo of the A converter.

Furthermore, the circuit of the embodiment shown in FIG. 1 is provided with resistors R and Rf, which serve as calculation coefficients when adding or subtracting analog signals. are all aligned to the same value.

Next, the operation of the multiplication type DA converter configured as described above will be explained. First, the analog input terminal V in 1 of one DA converter DACI has an analog input voltage Vi and a resistor Sum current (Vi+Vb')/R of current V i / R determined by R and current Vb/H determined by bias voltage vb and resistor R
flows and pours in. Further, only the current vb/R determined by the bias voltage vb and resistance R flows into the analog input terminal V in 2 of the other D-Af converter DAC2.

As a result, the conversion output terminal of one D-A converter DACI receives a signal f equivalent to the product of the sum current (Vi+Vb)/R and the digital value of the digital input signal Di.
i (V i +V b )/R flows in. In addition, the conversion output terminal of the other D-A converter DAC2 has a current Vb/R determined only by the bias voltage vb and the resistor R.
A current DiVb/R corresponding to the product of and the digital value of the digital input signal Di flows in.

Here, the current Di, ·Vb/R flowing into the reusable output terminal of the other D-A converter DAC2 is "operational amplifier A I
K, t: ``C opposite direction FIR flow-D i I
IV b/RK polarity is inverted. Then, this polarity-reversed current -Di-vb,/i't and one D-A
Conversion output current D i (■i+Vb
)/R are added together by an operational amplifier A2 having a feedback resistor Rf. In other words, the output of one D-A converter DAC1 (D i (V i + Vb )/R
) The conversion output of the other D-A converter DAC2 (Di・
Vb/R) is subtracted. The result of this subtraction (Di(V
t+vb)/R-D i IIVb/R=D i −
ViIIIRf/R) is the final analog output voltage V.

It is derived as The output voltage V obtained in this way
o is a voltage Di@Vi- corresponding to the product of the analog input voltage Vi and the digital input signal Di multiplied by each other.
Rf/R.

First, the analog input voltage Vi can take a negative polarity within the range of the absolute value of the bias voltage vb. This makes it possible to operate with respect to analog input voltage Vi of either positive or negative polarity.

The output voltage Vo is the analog input voltage V
The bias voltage vb can take either positive or negative polarity depending on the polarity of i.
Subtraction operation by 2 (Di(Vi+Vb)/R-Di@V
b, /R=Di·Vi@Rf/R%. As a result, the analog input voltage Vi and the digital input signal Di are
The final output voltage Vo (Vl
o=Di·Vi−Rf/R) can be obtained accurately.

As described above, the unipolar D-A can only operate with analog input signals of either positive or negative polarity.
A bipolar multiplier type D-A that can operate with analog input signals of either positive or negative polarity with a converter.
A transducer can be configured.

FIG. 2 shows a second embodiment of the multiplication type DA converter according to the invention.

The multiplying type D-A converter shown in the same figure has one D-A converter DAC117)7 in addition to the configuration of the first embodiment described above.
sl: Analog conversion output (Di(Vi+Vb)/R) of the other D-A converter DAC2
・When subtracting Vb/R), the analog input voltage V
It is characterized in that a value (V i /2 R) obtained by multiplying i by a certain coefficient is further subtracted and output.

Specifically, the analog input voltage Vi is connected to an operational amplifier A for subtraction operation via a resistor 2R in series for providing an operational coefficient.
It is only necessary to lead to the inverted input of 2.

As a result, the digital input signal Di becomes the maximum value FF(
If the value when the digital input signal Di takes the intermediate value 80 (hexadecimal display) is 1, then the final output voltage Vo is 0 (zero) JtC. -1/2) Vi ・Rf/R) can now be obtained. In other words, the digital input signal D51rC also has positive and negative polarities so that multiplication can be performed.

Table 1 below summarizes the relationship between the polarity of the analog input voltage Vi, the digital input signal DiO value, and the polarity of the output voltage Vo in the second embodiment.

Table 1: Polarity of Vi, Di, Vo As is clear from Table 1 above, the second embodiment operates as a complete four-quadrant multiplication type D-A converter.

FIG. 3 shows a third embodiment of the multiplication type DA converter according to the present invention, together with the characteristics of a portion thereof.

In addition to the configuration of the second embodiment described above, the multiplier type D-A converter shown in the same figure has a polarity (
The present invention is characterized in that the level of the bias voltage vb is gradually increased in accordance with the instantaneous level of the analog input voltage Vi when the voltage swings to the (negative) side.

Here, as shown in FIG. 3 (al indicates a specific circuit configuration thereof), a variable bias generation circuit 20 configured as shown in FIG. It is provided.

As shown in the same figure (bl), when the analog input voltage Vi is negative, the output voltage characteristic of this variable bias generation circuit 200A is always △V higher than the absolute value of the analog input voltage Vi.
When the analog input voltage Vi is positive, the D-A converter DAC1 generates a positive bias voltage vb higher than Vb.
, the minimum positive bias voltage △■ required to operate the analog input terminals Vinl and Vin2 of DAC2 normally.
It is supposed to only occur.

A specific circuit for obtaining such characteristics can be easily constructed using operational amplifiers A3 and A4, an input resistor R, a feedback resistor R1, a diode Df, etc., as shown in the same figure (cl). , multiplication type D- of the third embodiment
In the A converter, when the analog input voltage Vi swings to the negative side, the bias voltage vb increases to the positive side in response to this, thereby ensuring the polarity at the analog input terminal Vin of the D-A converter DAC1. You can move it to the positive side. This makes it possible to ensure a wide negative-side movement range, so-called dynamic range, of the analog input voltage Vi. Also, when the analog input voltage Vi swings to the positive side, with only this analog input voltage Vi,
The polarity at the analog input terminal V in of the D-A converter DAC1 can be maintained at an accurate positive side pressure. Therefore,
At this time, the bias voltage vb is set to the minimum necessary voltage ΔV to prevent the input current (Vi+Vb)/R of the analog input terminal Vinl from exceeding the input range of the input terminal Vinl.

Accordingly, it is possible to secure a wide movement range of the analog input voltage Vi on the positive side, a so-called dynamic range.

As described above, it is possible to ensure a wide dynamic range of the analog input voltage Vi in both the positive and negative directions, thereby allowing the D-A converters DACI and DAC2 to always operate with high resolution performance. is possible,
Therefore, highly accurate conversion operations can be performed.

〔effect〕

(1) Two unipolar multipliers with the same characteristics -A
A converter and a circuit for generating a bias signal having a valid polarity for the analog input terminal are provided, and when one D-A converter is busy, a digital input signal is input to its digital input terminal, and , inputs the sum of the analog input signal and the bias signal to its analog input terminal, and inputs the digital input signal to its digital input terminal, and inputs the sum of the analog input signal and the bias signal to its analog input terminal. By inputting only the bias signal and subtracting the analog output signal of one D-A converter from the analog output signal of the other D-A converter, the polarity of either positive or negative can be changed. The effect is that a multipolar D-A converter that can operate only with analog input signals of either positive or negative polarity can be configured with a unipolar D-A converter that can only operate with analog input signals of positive or negative polarity. can get.

(2) Furthermore, when the analog input signal swings to the polarity side where it becomes invalid with respect to the analog input terminal, the level of the bias signal is gradually increased in accordance with the instantaneous level of the analog input signal. This makes it possible to ensure a wide dynamic range of analog input signals in both positive and negative directions, which allows the D-A converter to always operate with high resolution performance, resulting in highly accurate conversion operation. K
You can get the effect that.

Although the invention made by the present inventor has been specifically explained above based on examples, it goes without saying that this invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Nor. For example, the multiplication type D-A converter may be manufactured by a C-MOS manufacturer.

[Application field]

The above explanation will mainly focus on the four-quadrant multiplication type D-A
Although the case where it is applied to converter technology has been described, it is not limited to this case. For example, a two-quadrant multiplication type D-A
It can also be applied to converter technology.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the multiplication type D-A converter according to the present invention, and FIG. 2 shows the operating characteristics of a part of the third embodiment of the multiplication type D-A converter according to the present invention. FIG. DESCRIPTION OF SYMBOLS 10...Digital signal generation part, 12...Clock pulse generator, 14...Cyclic counter, 16...Table measurement, Di...Digital input signal, Vi...
- Analog input signal (analog input voltage), DACI. DAC2...Unipolar multiplier type D-A converter, Dinl
. Din2=digital input terminal, V r M 1 , V
rM2...Analog input terminal, ■b...Bias signal () terminal voltage), R, Rf...Resistor, A1. A2
．． A3゜A4...analog operational amplifier, vO...analog output signal (analog output voltage), 20...bias generation circuit, Df...diode.

Claims (1)

[Claims] 1. A multiplier type D-A converter that outputs the product of a digital input signal and an analog input signal as an analog signal, which has a unipolar analog input that is effective only for either positive or negative polarity. Two multiplying type D-A converters having terminals with the same characteristics are provided, and a circuit for generating a bias coefficient having a polarity on the effective side for the analog input terminal, and one D-A converter is provided.
- For the A converter, input the digital input signal to its digital input terminal, and input the sum of the analog input signal and the above bias signal to its analog input terminal, and for the other DA converter, input the sum of the analog input signal and the above bias signal to its analog input terminal. While inputting the above digital input signal to the digital input terminal,
Only the bias signal is input to the analog input terminal, and the analog output signal of one D-A converter is subtracted from the analog output signal of the other D-A converter before being output. Multiplying type D-A converter. 2. When subtracting the analog output signal of one D-A converter from the analog output signal of the other D-A converter, the value obtained by multiplying the analog input signal by a certain coefficient is further subtracted and output. A multiplication type D-A converter according to claim 1, characterized in that the multiplication type D-A converter is configured as follows. 3. When the analog input signal swings toward a polarity side that is ineffective with respect to the analog input terminal, the level of the bias signal is gradually increased in accordance with the instantaneous level of the analog input signal. A multiplication type D-A converter according to claim 4 or 2.