SU830421A1

SU830421A1 - Logarithmiu sonverter

Info

Publication number: SU830421A1
Application number: SU792814336A
Authority: SU
Inventors: Радислав Васильевич Бегота
Original assignee: Львовский Ордена Ленина Поли-Технический Институт
Priority date: 1979-08-28
Filing date: 1979-08-28
Publication date: 1981-05-15

Description

(54) ЛОГАРИФМИЧЕСКИЙ ПРЕОБРАЗОВАТЕЛЬ(54) LOGICAL CONVERTER

II

Изобретение относитс к преобразовател м электрических сигналов по логарифмическому закону и может быть использовано в аналоговых вычислительных машинах.The invention relates to a transducer of electrical signals according to a logarithmic law and can be used in analog computers.

Известен логарифмический преобразователь , содержащий операционные усилители, логарифмирующие транзисторы, сумматор 1.Known logarithmic converter containing operational amplifiers, logarithmic transistors, adder 1.

Однако это устройство характеризуетс значительной погрещностью преобразовани .However, this device is characterized by a significant conversion error.

Наиболее близким по технической сущности и достигаемому результату к предлагаемому вл етс логарифмический преобразователь , содержащий первый и второй операционные усилители, к инвертирующим входам и выходам которых подключены соответственно коллектор и эмиттер соответствующих логарифмирующих транзисторов , базы которых соединены с щиной нулевого потенциала, инвертирующий вход первого операционного усилител через первый масщтабный резистор присоединен ко входу логарифмического преобразовател , к инвертирующему входу второго операционного усилител подключен первый вывод второго масщтабного резистора, выходыThe closest in technical essence and the achieved result to the proposed is a logarithmic converter containing the first and second operational amplifiers, to the inverting inputs and outputs of which are connected respectively a collector and an emitter of the corresponding logarithming transistors, the bases of which are connected to a zero potential, the inverting input of the first operational amplifier through the first scaling resistor is connected to the input of a logarithmic converter, to the inverting input of the second the first operational amplifier is connected to the first output of the second scale resistor, the outputs

первого и второго операционных усилителей соединены с соответствующими входами суммирующе-вычитающего блока, сумматор, выход которого вл етс выходом логарифмического преобразовател 2.the first and second operational amplifiers are connected to the corresponding inputs of the summing-subtracting unit, the adder, the output of which is the output of the logarithmic converter 2.

Недостаток этого устройства - погрешность передаточной характеристики, привод ща к снижению точности работы.The disadvantage of this device is the accuracy of the transfer characteristic, leading to a decrease in the accuracy of operation.

Цель изобретени - повышение точности преобразовани .The purpose of the invention is to improve the accuracy of the conversion.

Поставленна цель достигаетс тем, что в преобразователь введены ключевой элемент и источник опорного напр жени , приче .м выход источника опорного напр жени подключен к третьему входу суммирующевычитаюшего блока, выход которого через ключевой элемент соединен с первым входом сумматора, второй вход которого присоединен к выходу первого операционного усилител , управл ющий в.код ключевого элемента соединен со входом логарифмического преобразовател и со вторым выводом второго масштабного резистора.The goal is achieved by introducing a key element and a voltage source into the converter, the output of the voltage source being connected to the third input of the summing reading unit, the output of which is connected to the first input of the first through a key element an operational amplifier, the control V. code of the key element is connected to the input of a logarithmic converter and to the second output of the second large-scale resistor.

На чертеже изображена функциональна схема преобразовател .The drawing shows the functional diagram of the Converter.

Claims

The converter contains the first and second scale resistors 1 and 2, the first and second operational amplifiers 3 and 4, the first and second logarithm transistors 5 and 6, the on-voltage source 7, the summation-subtraction unit 8, the key element 9, the adder 10, the bus 11 zero potential, input 12 and output 13 of the logarithmic converter. The logarithmic converter works as follows. A change in voltage at input12 of a logarithmic converter leads to a change in the collector current of the first logarithmic transistor 5. The output voltage of the first operational amplifier 3 changes in proportion to the logarithm of the collector current of the first logarithmically transistor 5. As the collector current increases, the error from the voltage drop on the volume increases. the base impedance of the first log-uouiei-Q transistor 5, which leads to an increase in the output voltage of the first operational amplifier 3 rank of this voltage drop. The resistance of the second large-scale resistor 2 is chosen greater than the resistance of the first large-scale resistor 1, so that at the end of the operating range, at the maximum collector current of the second logarithm transistor 6, the voltage drop / on the volume resistance of the second logarithm of the transistor 6 on the output voltage of the second operational amplifier is E5 4 was small. It is necessary that the first and second logarithm transistors 5 and 6 have almost identical parameters. Then the output voltage of the summing-subtracting unit 8 contains only the error voltage of the first logarithmic transistor 5. With relatively small values of the voltage at the input 12 of the logarithmic converter, when the voltage of the error of the first logarithmizing transistor 5 can be applied to the output voltage of the first operational amplifier 3 ignore, the key element 9 is open and the adder 10 transmits the output voltage of the first operational amplifier 3 to the output 13 of the logarithmic converter without measuring Genii. As the voltage at input 12 of the logarithmic converter increases, the error voltage also increases. At the same time, this component is also present at the output of the summing-subtracting unit 8. A key element 9 is closed at a certain voltage level at input 12 of the logarithmic converter. As a result, adder 10 subtracts the total error of the first logarithmic transistor 5 from the total voltage signal 13, a logarithmic converter forms a voltage proportional to the logarithm of the collector current of the first logarithmic transistor 5 without the component fault voltage. Thus, in the proposed logarithmic converter, the voltage drop across the volume resistance of the base of the first logarithmic transistor 5 in the output voltage of the first operational amplifier 3 is compared by comparing this voltage (using the second operational amplifier 4 and the second logarithmic transistor 6) to its "ideal value, the subsequent allocation of the voltage gap by using the summation-subtraction unit 8 and the summation of the output voltage of the first operating 3, which contains the error voltage, with its selected inverted value with the help of adder 10 at a certain moment, associated with the closure of the key element 9. The present invention reduces the error in the transfer characteristic of the converter. A logarithmic converter comprising first and second operational amplifiers, the inverting inputs and outputs of which are connected respectively to the collector and emitter of the corresponding logarithm transistors, the bases of which are connected to a zero potential, the inverting input of the first operational amplifier through the first scale resistor connected to the input of the logarithmic converter the first output of the second large-scale re is connected to the inverting input of the second operational amplifier the outputs of the first and second operational amplifiers are connected to the corresponding inputs of the summing-subtracting unit, the adder, the output of which is the output of a logarithmic converter, characterized in that, in order to improve the accuracy of the conversion, a key element and a source of reference voltage are introduced into it, moreover, the output of the reference voltage source is connected to the third input of the summing-subtracting unit, the output of which is connected via a key element to the first input of the adder, the second input of which is connected To the output of the first operational amplifier, the control input of the key element is connected to the input of the logarithmic converter and to the second output of the second large-scale resistor. Sources of information taken into account in the examination 1. UK Patent No. 1333287, cl. G 4 G, pub. 1973.

2. USSR author's certificate according to application number 2795493 / 18-24, cl. G 06 G 7/24, 10.07.79 (prototype).