SU1238113A2 - Logarithmic converter - Google Patents

Abstract

The invention relates to the field of analog type APS technology and can be used in multiplier-dividing devices for compressing and expanding dynamic. range of input signals, and can also be used in the circuits of instrumentation equipment. The purpose of the invention is to improve accuracy. The converter contains a operational amplifier, a main transistor, n additional transistors, and a differential operational amplifier, a large-scale resistor, and p, rectifying transistors. In the proposed logaric converter, the presence of cascade-connected correction transistors makes it possible to compensate for an increase in the output voltage, since in this case the base currents of the primary and additional transistors will not be added to their collector currents. In the case of the dependence of the converter on the implementation of exp x, the collector current of the transistors is an exponential function of the voltage U, g. 1 il. . (ABOUT

Description

The invention relates to analog computing and can be used in multiplying-dividing devices for compressing and expanding the dynamic range of input signals, as well as in instrumentation circuits.

The purpose of the invention is to improve accuracy.

Fig. L is a functional diagram of the proposed logarithmic converter; FIG. 2 is a functional diagram for implementing dependency at exp.

Logary} 1 converter. Contains operational amplifier 1, main transistor 2, n additional transistors 3, - 3, n differential operational amplifiers A (- 4, scale resistor 5, n corrective transistors 6 - 6 ",

The logarithmic converter works as follows.

The main transistor 2, n additional transistors 3–3 n and n correcting transistors must have the same parameters, which is practically performed if they are manufactured using the same technology in a single chip. Therefore, it is permissible to assume that the coefficients are increased by the current .. the transistor is almost the same. Under the influence of the input voltage 11 in the feedback circuit of the main operational amplifier 1, a current flows causing voltage drops at the emitting junctions of the main 2 and additional 3, Bc transistors, the sum of which is equal to the output voltage Ugy of the converter. The presence of cascade-connected correction transistors 6 "- 6 (allows you to compensate for the increase in voltage and, because in this case the base currents of the main 2 and additional

381132

3 to 3 transistors are not summed with their collector currents associated with the voltage across the emitter junction. ,

  , s- fi / -; 7- -i.-nf- -

. er where RJ is the scale resistance.

resistor 5; to fi 8 parameters of the transistor;

i is the collector current of the transistor. The output voltage of the converter is

"5 out

-n.y, / - ncf.i, (| -v; g)

(2)

In the case of the implementation of the dependency EX exp X - the operation of the circuit is similar to that mentioned above, only the collector current of the transistors is an exponential function of the voltage U, therefore

II - TJ - - - t

and

Out

- H

 e

- RV fiiii .ll. V.4 n

(3)

formula of iso e and a

Logari4michey converter avt.St. (R 631940, about tl and h and u and with the fact that, in order to increase the accuracy, it has been introduced into the base of the pieKTHpinonxx transistors, and

the base of each i-th (i “1,2, ..., p) correcting transistor is connected to the non-inverting input of the corresponding differential operational amplifier, KoiineKTOp of the first

the correcting transistor is connected to the zero potential bus, the emitter of each th correcting transistor is connected to the collector (i - “- l) of the correcting T1) anzistor,

The emitter of the nth correction transistor is connected to the output of the converter.

I

F1 / g.1

fffur.

Compiled by I.Zaitsev Editor S.Lisin Tehred N. Bonkalo Proofreader A.Obruchar

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VNISh State Committee of the USSR

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4

Claims (1)

formula from b'ret e nor i Logarithmic converter for auto No. 631940, with root and the fact that, in order to increase accuracy, η cor- is introduced into it. rectifying transistors, and the base of each ΐ -th (<"1,2 ,,"., n) correction transistor is connected. to the non-inverting input of the corresponding differential operational amplifier, the collector of the first 40 correction transistor is connected to the zero potential bus, the emitter of each ίth correction transistor is connected to the collector (i + Ι) of the correction transistor, 45 emitter of the ηth correction transistor is connected to the output of the converter.