SU834769A1 - Analogue storage - Google Patents

Description

(54) ANALOG STORAGE DEVICE

one

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

Devices for memory and voltage are known that contain a capacitor in the input circuit of amplifier 1.

 However, such devices have low accuracy due to the bias voltage drift of the amplifier.

The closest in technical essence to the present invention is an analog storage device with offset voltage drift compensation, containing a capacitor, an amplifier and three switches, the sub-contacts of the first and second switches are connected to the capacitor plates, the movable contact of the third is to the amplifier output, one of the fixed the contacts of the first switch are connected to the input of the device, one of the fixed contacts of the second is connected to the output of the amplifier, one of the fixed contacts of the third is connected to the common bus, THER fixed contacts of the first and third switches connected between .soboy, another fixed contact

the second switch is connected to the common bus 2.

The disadvantage of such a device is low accuracy and speed.

In the recording (sampling) mode, the capacitor is connected by one plate to the signal source, and the other is connected to the output terminal of the amplifier. On the equivalent output resistance of this clamp RQ, the voltage drops, which determines the error in the undercharging of the capacitor

cr; .i / ci zjRp ;,

five

where Zj.- capacitance of the capacitor.

0

The minimum error corresponds to the inequality, T.e. It is necessary to use amp with mi. minimum output impedance.

five

On the other hand, direct connection of a capacitor to an input source causes shunting of the latter and, as a result, a decrease in accuracy. The resulting error is expressed by the formula (with)

, .- f / (t.,

where Rp is the internal resistance of the input source. Since (6.28 fpC), the error is higher, the greater the frequency of the signal f (, and the capacitance, of the capacitor C. In this case, the speed of the known device is determined by the time constant

)

The purpose of the invention is to improve the accuracy and speed of the device.

The goal is achieved by the analog storage device containing an amplifier covered by the inverting input feedback, a storage element, such as a capacitor, one of the plates of which is connected through the first break contact with the output of the amplifier and device, and through the first closing contact bus zero potential, the second break contact, the second and third closing contacts, the other capacitor lining connected through the second break contact with the tire of zero potential, and through the second closing contact is with the non-inverting input of the amplifier, the device input is connected via the third closing contact to the non-inverting input of the amplifier.

The drawing shows a functional diagram of the proposed device. It contains a storage element, for example, capacitor 1, amplifier 2 soaking contacts 3 and 4, closing contacts 5-7 and zero potential bus 8 (in the drawing only contacts that may belong to switches, keys, etc.) are conventionally shown.

The device operates as follows.

In the recording (sampling) mode, contact 7 is closed, capacitor 1 is connected by pins 3 and 4 to the output of amplifier 2 and to the potential-free bus. Capacitor 1 is charged before voltage is applied.

Uc% lTr- o) r (

where Ugj (is the voltage of the signal source;

U0 is the bias voltage of the amplifier.

Since in order to increase the accuracy of analog storage devices, the transmission coefficient for a voltage-amplified open-loop amplifier is; much more than one is chosen; then K / (1 + K) 1 and expression (1) takes the form

(tUo)

(2)

, At the same time, the signal source is connected to the input of amplifier 2, encompassed by a 100% feedback on the noninverting input. As a result, high input and low output impedance of the amplifier is achieved. This excludes shunting of the signal source and the forced charging of capacitor 1 by the output current of amplifier 2. And the difference from the known device

5 The constant charge of capacitor 1 is g., (Where C is the capacity of the on-capacitor 1), and since the expression does not include the internal resistance of the input source Rp /

11 ngshnogo higher than a small value of the SHINDTING resistance of the amplifier 2 Qf then the speed of the proposed device can exceed the speed by several orders of magnitude

“A new device.

In the storage mode, the contact 7 is opened, and the capacitor 1 is switched by contacts 6 and 5 in such a way that the plate of the capacitor 1, which was under bus potential

0 8, is connected to the non-inverting input of amplifier 2, and the capacitor plate 1, which is under potential Uc, is connected to bus 8. The output voltage of the analog

5, the storage device is

you.) smiling)

Q where is the bias voltage of the amplifier 2 at the moment of transition from the recording mode to the storage mode.

Expressions (2) and (3) show the ca. uj compensation, because

(d) -iV-W - (iUo) -Ue.

Thus, at the output of the device in the storage mode, there is an inverted sign of the memorized input signal.

The achieved positive effect distinguishes the proposed device from the known. The high speed and accuracy of the device allows achieving high throughput of information processing of such devices as data acquisition systems, analog-digital converters, high-speed digital communication systems.

Claims (2)

1., Vakhtiarov g. The device of sampling and memorization: the principles of fasting, multiplication, the state of development and the prospects for development. - Foreign electronics, 1078, 10. 2. Authorship certificate of the USSR 461453, cl. G 11 C 27/00, 1974 (proto® t "t). Oh. g-ch