SU1406728A1 - Device for discrete control of gain - Google Patents

Abstract

The invention relates to instrumentation. The purpose of the invention is to improve accuracy. The device contains operational amplifiers (OA) 1 and 7. L-shaped voltage divider 2, made of resistor 3 and circuits 4, consisting of resistors 5 and switches 6, as well as circuits 8 and P, consisting of resistors 9 and 12 and switches Yu and 13, resistors 14 and 15 and feedback resistor 16. OU I is always covered by negative feedback regardless of the state of the keys 6, which does not allow the OU I to go to the saturation region when keying the switches. The goal is achieved by reducing the influence of public key resistance on the accuracy of the coefficient. gain 1 il.

Description

(L

05

 to

OS

"to

The invention relates to instrumentation, namely, to measuring equipment, and can be used in analog and analog-digital measuring converters.

The purpose of the invention is to improve accuracy.

The drawing shows a circuit diagram of the proposed device.

The device with discretely controlled gain factor contains a main operational amplifier 1, an L-shaped divider 2 voltage, with a first resistor 3 and parallel circuits 4, 42, ..., 4, each of which contains a main resistor 5 and primary switch 6, additional operational amplifier 7, second additional circuits 8 |, 82, ..., 8n, each of which contains the first additional resistor 9 and the first additional switch 10, the second additional circuits 11 |, -, ..., 11 “, Each of which contains a second additional resistor 12 and a second dopol key 13, second and third resistors 14 and 15, and feedback resistor 16.

The device works as follows.

The voltage value Ud at the output of the main operational amplifier 1 when the signal "1" is applied to the control input of the main switch of the first circuit

Ud U-Kpi, where and is the value of the input voltage;

Kp1 - the value of the real ratio

gears for the first stage, and

K „, 1 +

R-

R2 +

resistance values of the first resistor 3 and the main resistor 5;

value of the forward resistance of the primary key 6 of the first circuit 4 | in a closed state.

voltage at point

0

five

where ua i-p-tsnz -

K2 + K / I

connecting the main resistor 5 and the main switch 6 of the first circuit 4i;

Ka - -f--,

9,

Kd -f,

where Rg., is the resistance value of the first additional resistor 9 of the first additional circuit 8i;

R4 is the resistance value of the second resistor 14;

Кз is the resistance value of the third resistor 15.

To compensate for the input currents of the additional operational amplification 7, 1 second additional circuits Ih, ..., 11 are connected to its non-inverting input.

In this way, the influence of the resistance of the public keys on the accuracy 0 of the gain setting is reduced. The main operational amplifier 1 is always covered by negative feedback, regardless of the state of the main keys 6, which prevents the main operational amplifier 1 from entering the saturation region when switching keys.

The choice of one of the possible gain factors is achieved by applying the signal "1 to one of the control inputs -

Claims (1)

Invention Formula A device with discrete-controlled gain, containing an operational amplifier, the non-inverting input of which is the device input, and the L-shaped voltage divider, in the long arm of which the first resistor is connected, in the transverse - n parallel-connected circuits, each in the form of series-connected main resistor and main switch, with the longitudinal shoulder of the L-shaped voltage divider connected between the output and the inverting input of the operational amplifier, and the transverse between the inv rtiruyuschim input of the operational amplifier and ob5 0 0 tandem bus, the control inputs of the keys in the closed main key 6 first. are the control inputs of the device, characterized in that, in order to increase the accuracy, an additional operational amplifier with a feedback resistor connected between the output and the inverting input of the additional chain 4 | closed the first and second additional keys 10 and 13 of the first and second additional chains 8 | and 11. In this case, the voltage Ua, falling on the direct resistance of the main key 6 of the first circuit 4 |, through the first additional key 10 50 of operational amplification, the first additional additional first circuit 8i of the feed circuits, each containing the inverting input of the additional additional pre-operative amplifier 7 sequentially connected to each black resistor and the first additional switch, the second additional containing each successively a coupling amplifier 1, with a voltage of the second additional resistor Jg at the output of the additional opera and the second additional key and also the amplifier 7 has a resistor connected between the output the main operational amplifier and the inverse; the second resistor 14 also supplies the voltage Ud from the output of the main operation UdKd + Ua-Ka, , 1406728. five The operative circuit is between the point of the coupling amplifier, and the third resistor, including the main resistor with a key in the coupling between the non-inverting input of the p circuits and the inverting input of the additional operational amplifier and the additional operational amplifier. The common additional, while the second additional and control inputs of the first and second data circuits are connected between the non-inverting-full YouTube terminals connected to the corresponding input of the additional operational-specific control inputs of the oral amplifier and the common connections.