JPS62155622A - Digital-analog converter - Google Patents

Abstract

PURPOSE:To decrease the settling time and to attain high speed operation by supplying an inverting current output of a current output circuit to a differentiation circuit, inverting the polarity of the output of differentiation circuit and adding the result to an output current of the current output circuit. CONSTITUTION:The output of the current output circuit 14 is fed to an adder circuit 21 and also the differentiation circuit 24. The output of the differentiation circuit 24 is fed to the adder circuit 21, whose output is fed to a current voltage conversion circuit 12. When input digital signals D1-Dn are changed and an output of the current output circuit 14 changes stepwise, a pulse B is obtained from the differentiation circuit 24 at the point of time of change. The pulse B is added to the output of the current output circuit 14 by the adder circuit 21 in a way of the addition in its changing direction. Then the addition output C is fed to the current voltage conversion circuit 12, its output D is changed in response to the output change of the current output circuit 14. When the output of the current output circuit 14 changes stepwise in this way, since a differentiation pulse increasing the change is superimposed on the output of the current output circuit 14, the settling time of the current voltage conversion circuit is reduced and the DA converter with higher speed is obtained by the reduction.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention outputs a current of a magnitude corresponding to digital human power from a current output circuit, converts the output current into voltage with a current-voltage conversion circuit, and outputs it. This invention relates to a DA converter.

"Prior Art" A conventional DA converter was constructed as shown in FIG. Digital human power D1-Dn from input terminals 1)-ln is supplied to gates 21-2n, respectively, and each has a predetermined weight.

One current path of each of the current switching circuits 31 to 3n is grounded, and the other current path is connected to the common constant current source 1) and to the input terminal 13 of the current-voltage conversion circuit 12.

Gates 2, ~2n, current light current paths 3□~3rl, and constant current source 1) constitute a current output circuit 14, and input terminals 1)~l
A current switching circuit 3 according to the digital inputs D1 to D of o.
~3n are controlled, and the current flowing to the current switching circuits 3 and ~3n side and the output current I flowing to the current-voltage conversion circuit 12 side. Which sum is the constant current of the constant current source 1)■. , so that (
=, output current I. flows, so the output current I. is a value according to the digital input. This output current■. The current is converted into a voltage by the magnetic pressure conversion circuit 12 and output to the output terminal 15.

A parasitic resistance ro and a parasitic capacitance C are provided on the output side of the current output circuit 14.
In order to stabilize the operation, the time constants of the feedback resistor 16 and capacitor 17 of the current-voltage conversion circuit 12 must match the time constants of the parasitic resistance r and the parasitic capacitance C0. Therefore, in this conventional DA converter, the current output circuit 1
Even if 4 has an ideal step response to changes in the input digital signals D1 to Dn, due to the band limitation of the resistor 16 and capacitor 17 in the current/magnetic pressure conversion circuit 12 and the band limitation of the operational amplifier 18, It does not respond stepwise to changes in the input digital signals D1 to Dn, and when the human power changes, the settling time until the output corresponds to that human power is relatively long, making it possible to operate at high speed. It was difficult.

"Means for Solving the Problem" According to this invention (2), the inverted current output of the current output circuit is supplied to a differentiating circuit, and the output of the differentiating circuit is polarized and added to the output current of the current output circuit. .

When the input digital signal changes, the inverted DC output of the current output circuit instantly changes to the corresponding value.
Therefore, a differential pulse is obtained from the differentiating circuit, and this pulse is inverted in polarity and applied to the current output circuit, so the output current of the current output circuit is:

The change in the human-powered digital signal is instantaneous, but a differential pulse is added to make the change even larger. This addition of differential pulses acts to speed up the response of the current-voltage conversion circuit.

(Cera) The IJn gamma time is shortened and high-speed operation is possible.

``Example'' FIG. 1 shows the principle of this invention. The output of the current output circuit 14 is supplied to an adding circuit 21 and also to a differentiating circuit 22. The output of the differentiating circuit 22 is supplied to the adding circuit 21, and the output of the adding circuit 21 is supplied to the current-voltage conversion circuit 12.

The input digital signals D1 to Dn change and the current output circuit 1
When the output of 4 changes stepwise as shown in FIG. 2A, a pulse as shown in FIG.
Adding circuit 2 is added to the output of , in the direction of change.
1, and the addition output is as shown in Figure 2C, (
2, this is supplied to the current-voltage conversion circuit 12, and the output of 7 changes according to the change in the output of the current output circuit 14, as shown in the second ['lD, but the change is somewhat rounded. .

However, if the outputs of the differentiating circuit 22 are not added, that is, only the output shown in FIG.
In the case of supplying the same amount of energy to the 100%, as shown by the dotted line in the second diagram, the change in the change becomes very blunt; however, in the present invention, this blunting can be reduced. In the current-voltage conversion circuit 12, the polarity is reversed between input and output in the specific circuit shown in the sixth □□□.

The delay in the change in output of the current-voltage conversion circuit 12 relative to human power can be regarded as a first-order lag circuit, and its transfer function can be expressed as 1+Sτ0. Assuming that the differentiating circuit 22a'CR is the differentiating circuit, its transfer function is as follows. τd is the time constant of C and H. Therefore, the current-voltage conversion circuit 12. The overall transfer function G(S) of the differentiating circuit 22 and the adding circuit 21 is as follows. 2τd=τ. Then, G(S) becomes. As can be understood by comparing Equation (5) and Equation (1), under the condition of 2τd=τ0, the circuit shown in itg has a conventional The response speed is doubled compared to the circuit.

The third factor shows an embodiment of the present invention, and parts corresponding to those in FIG. 6 are given the same reference numerals. In this embodiment, the current path 23 of each current switching circuit 3□ to 3rI of the current output circuit 14 is connected to a current differentiation circuit 24. The output side of the current differentiating circuit 24 is connected to the input terminal TF-13 of the current-voltage conversion circuit 12 through a signal' inversion circuit 25. In the current differentiation circuit 24, the current path 23 of the current switching circuit is grounded through a resistor 26 and a capacitor 27? : Connected through the signal inverting circuit 25 (-).

In the signal inverting circuit 25, the capacitor 27 is connected to the constant abrasive current source 28 (== connected to the emitter of the transistor 29, the base of the transistor 29 is grounded,
The collector is connected to the collector of transistor 31, the base of transistor 3 is connected to the collector of transistor 3, and also to the base of transistor 32, and the emitter of transistor 31, 32 is connected to the positive power supply terminal through resistor 33, 34Y. 35. The collector of transistor 32 is connected to input terminal 13 .

In this configuration, the output current Io is supplied to the input terminal -13 of the current output circuit 14, and the output current Io is supplied to the differentiating circuit 24. The flow direction is opposite, but the absolute value is the same. This change in output current Io is differentiated by a differentiating circuit 24,
The direction of change of the differential output is inverted by the signal inverting circuit 25 and superimposed on the output current I0. For example, output dragon flow engineering. When increases stepwise, the output current I. decreases stepwise and increases unless the direction is considered), and the differential of the differential circuit 24 increases.
The minute pulse flows from the transistor 29 to the capacitor 27 side.

The current pulse flows through the transistor 31, so that the collector current of the transistor 32 increases in a pulsed manner, and this current becomes the current I. and is supplied to the current-voltage conversion circuit I2. The transistor 29 lowers the impedance, and the potential fluctuation of the collector of the transistor 31 is changed to the current path 2.
It acts to prevent any influence on the third side.

The gain of the signal inversion circuit 25 is adjusted, that is, the resistor 33.
By selecting 34 resistance values, it is possible to adjust the pulse current value added to the current Io.

If there is a possibility that the potential fluctuation of the current path 23 may occur due to the connection of the differentiating circuit 24''k to the current path 23, the differentiating circuit 24 may be connected via the buffer circuit 37 as shown in the fourth factor.

The current path 23 is connected to the collector of a human-powered transistor 38 constituting a current mirror circuit in the buffer circuit 37 (connected to two constant current sources 39).

The collector of the output transistor 41, which together with the transistor 38 constitutes a current mirror circuit, is connected to the collector of a transistor 42, which together with the transistor 43 constitutes a current mirror circuit. However, in this case, resistors 44 and 45 are inserted in series with each emitter of the transistors 42 and 43 so that a constant ratio can be obtained between the output currents. can be selected. The collector of the transistor 43 is connected to the input side of the differentiating circuit 24.

When the current o in the current path 23 increases jJD, the current in the transistor 38 increases, and therefore the current in the transistors 41 and 42 also increases, and the current in the transistor 43 also increases.The differential current due to this increase is the signal Inversion circuit 2
Differential capacitor 27 from transistor 46 in 5. Current flows through transistor 43. The collector of the transistor 46 is connected to the input terminal of the current mirror circuit 47 in the signal inversion circuit 25, the output side of the current mirror circuit 47 is connected to the input terminal 'T-13, and the connection point between the capacitor 27 and the transistor 46 is connected to the input terminal of the current mirror circuit 47 in the signal inversion circuit 25. 48 to the input side of a current mirror circuit 49, and the output side of the current mirror circuit 49 is connected to the input terminal 13. The bases of transistors 46, 48 are grounded. The difference between the currents flowing through the current mirror 1) jlj147.49 is input to or output from the input terminal 13. As described above, when the current IO increases, the current flowing through the transistor 43 also increases, and current flows into the capacitor 27 from the transistor 46 in a pulsed manner.

This pulse current is passed from the current mirror circuit 47 to the input terminal'
:Supplied to F-13.

In the above description, the current value 0 of the current path 23 is supplied to the current differentiation circuit 24, but a voltage differentiation circuit may also be used. Fifth
The figure shows an example. The current path 23 is grounded through a resistor 51, and the voltage generated by the resistor 51 is supplied to a voltage differentiator circuit 53 through a buffer circuit 52. In this example, the output of the differentiating circuit 53 is supplied to the non-inverting input terminal of the operational amplifier 18 in the current-voltage conversion circuit 12, and the input terminal 13 is connected to the inverting input terminal of the operational amplifier 18. This is a case where the output is inverted and added to the input of the input terminal T-13 within the current-voltage conversion circuit 12.

"Effects of the Invention" As described above, according to the DA converter of the present invention, when the output of the current output circuit 14 changes stepwise, the differential pulse in the direction of increasing the change is transmitted to the current output circuit 14.
Because it is superimposed on the output of 4.

The settling time of the current-voltage conversion circuit can be reduced, and a DA converter that operates at high speed can be obtained. Moreover, since the current in the inverted current path 24 of the current output circuit is used and processed in an analog manner by an analog differentiating circuit, there is an advantage that a single circuit configuration is extremely simple.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the principle of this invention, the second factor is a time chart for explaining Fig. 1, Fig. 3 is a connection diagram showing an embodiment of this invention, the fourth factor and the fifth factor. Each figure is a connection diagram showing an example of the pond of the present invention, and FIG. 6 is a connection diagram showing a conventional DA converter. 1) ~ln=digital signal input terminal, 3, ~3o: current switching circuit, 12: current voltage conversion circuit, 14: current output circuit, 24: current differentiating circuit, 25: signal inversion circuit, 47
, 49: Current mirror circuit, 53: Voltage differentiator circuit. Patent applicant: Atopantest Co., Ltd. Agent
Takuo Kusano 1 Figure 2 Master 6 Figure 6 procedural amendment (voluntary) February 28, 1985 1, Indication of case Patent application 1987-2957942, Title of invention DA converter 3, Make amendment Relationship with the patent applicant case Atopan Test 4, Agent: Sagami Building 5, 4-2-21 Shinjuku, Shinjuku-ku, Tokyo, Subject of amendment Detailed description of the invention in the specification and drawing 6, Amendment The content of 1+S τ. (2) “Equations (3) and (4)” on page 6, lines 7 and 8 of the same book
The next 1+Sτd l+Sτ. (1+Sτd) (1+Sτ.) (3) “Formula (5)” on page 6, line 10 of the same book is corrected as follows. (4) Same book, p. 8, lines 14-17 “The transistor 29...
・・・It is working. "The transistor 29 has the function of lowering the input impedance to prevent potential fluctuations at the output terminal of the current differentiating circuit 24."
I am corrected. (5) Figure 1 of the cylinder in the drawing is corrected to the attached figure. that's all

Claims (1)

[Claims] (1) In a DA converter that has a current output circuit that outputs a current of a magnitude according to a digital input, and a current-voltage conversion circuit that converts the output current of the current output circuit into voltage, an inversion of the current output circuit described above. A DA converter comprising: a differentiating circuit to which a current output is supplied; and an adding means for inverting the polarity of the differential output of the differentiating circuit and adding it to the output current of the current output circuit.