JPH03185931A - A/d converter circuit - Google Patents

Abstract

PURPOSE:To improve the accuracy of A/D conversion by providing a compensation circuit and supplying a base current to a transistor(TR) of an input section of each comparator to prevent the production of an error component in the division of a reference voltage, thereby applying accurate division. CONSTITUTION:A comparator 6 supplies a base current to a base of TRs of an input section of each comparator and the current flowing to the entire reference resistor group 3 from a reference voltage terminal 1 is made identical. Thus, no error component due to a base current is generated in the divided voltage and an accurate comparate level is obtained. That is, the circuit 6 is constituted of TRs and current mirror circuits equal to those of the input section of the comparator and a base current is supplied to the TRs of the input section of each comparator. Thus, an input analog signal is compared with each accurate division voltage at each comparator to obtain a digital value with high accuracy and power consumption is saved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a parallel comparison type A-D converter circuit.

[Conventional technology]

FIG. 2 (alij) shows a circuit configuration of an example of a conventional parallel comparison type AD converter circuit.

In the figure, 1 is the reference voltage terminal, 2 is the analog signal input terminal,
3 is a reference resistance group, 4 is a comparator circuit group, 5
is an encoding circuit.

The reference voltage Vref is divided by the reference resistor group 3.

Each comparator circuit of the comparator circuit group 4 is compared with the input analog signal □ and each divided voltage.

A number of comparator circuits invert the output depending on the level of the input analog signal at each instant. The number of comparator circuits that invert the output of each clock signal is captured, and the encoder circuit 5 converts this into a binary number to obtain a digital value.

FIG. 2(b) shows the circuit configuration of the input section of the converter circuit which is connected to the A-D converter circuit of FIG. 2(a).

[Problem to be solved by the invention]

In the conventional parallel comparison type A-D converter circuit as described above, as shown in FIG. 2(b), the reference resistor group 3
Current flows through each comparator circuit, and an error component occurs in the divided voltage due to the current amplification factor.

There was a problem that accurate Nakonno 4 rate level could not be obtained.

Let the current flowing from the reference voltage terminal 1 be iH.

The level of each divided voltage is set sequentially from the highest level. So, the level of the n@th divided voltage from the highest level is.

As described above, ■N is the error component (n-1)!・1b-R occurs.

The present invention has been made to solve the above problem, and an object of the present invention is to provide a circuit in which no error component occurs in one divided voltage.

[Means for Solving the Problems] The parallel comparison type A-D converter circuit of the present invention compensates for error components occurring in the divided voltage due to the comparator input current flowing from the reference resistor circuit to each comparator circuit of the comma-four regulator circuit group. Lutame, Konno J? Detects the base current of the transistor in the input part of the transistor whose characteristics are the same as that of the transistor in the input part of the regulator circuit,
Current mirror circuit K, 1: J A compensation circuit is provided for supplying a current corresponding to the base current to the input of each comparator circuit of the comparator circuit group.

〔Example〕

FIG. 1(a) shows a circuit configuration of an embodiment of the present invention.

In the figure, 1.2, 3.4, and 5 indicate the same or corresponding parts as the same reference numerals in FIG. This is a compensation circuit.

FIG. 1(b) shows the circuit configuration of the input section of the conglomerator circuit in the embodiment of FIG. 1(a), and FIG.
The circuit configuration of the compensation circuit 6 in the embodiment of FIG. 3(a) is shown.

In the compensation circuit 6, the base current flowing into the base of the transistor in the input section of each comparator circuit and the current flowing through the entire resistor group 3 are equal to ib.

An error component due to the base current ib is no longer generated in the divided voltage. Therefore, an accurate conno f rate level can be obtained.

The compensation circuit 6 is composed of a transistor that is the same as the input section of the comparator circuit and the same transistor as a constant current circuit, and supplies a base current to the transistors at the input section of each converter circuit and the regulator circuit.

The input analog signal is compared with each accurate divided voltage in each comparator circuit to obtain a highly accurate digital value.

〔Effect of the invention〕

As described above, according to the present invention, there is an advantage that the reference voltage can be accurately divided and highly accurate A-D conversion can be realized.

Furthermore, in the past, an excessive current was passed through the reference resistor group in order to prevent accuracy deterioration, but the present invention eliminates the need for this, resulting in power savings.

[Brief explanation of drawings]

FIG. 1(a) is a circuit diagram showing the circuit configuration of an embodiment of the present invention, and FIG. 1(b) is a circuit diagram showing the circuit configuration of the input section of the comparator circuit in the embodiment of FIG. 1(a). . Figure 1 (cl) is a circuit diagram showing the circuit configuration of a compensation circuit applied to the embodiment of Figure 1 (a), Figure 2 (&) is a circuit diagram of an example of a conventional parallel comparison type A-D converter circuit. The circuit diagram shown in FIG. 2 (bl is a circuit diagram showing the circuit configuration of the input section of the comparator circuit applied to the A-D converter circuit of FIG. 2 (aJ). l...Reference voltage terminal, 2... Analog signal input terminal, 3
. . . reference resistance group, 4 . . . comparator circuit group, 5 . . . encode circuit, 6 .

Claims (1)

[Claims] A circuit that encodes the number of comparator circuits whose outputs are inverted for each instantaneous level of the input analog signal by comparing the input analog signal and each voltage obtained by dividing the reference voltage by the reference resistor group using a group of comparator circuits. In a parallel comparison type A-D converter circuit configured to convert into a binary number at , the input of the comparator circuit is A compensation circuit is provided in which the base current of the transistor in the input part is detected by a transistor having the same characteristics as the transistor in the part, and a current corresponding to the base current is supplied to the input of each comparator in the comparator circuit group by a current mirror circuit. A- characterized by
D converter circuit.