RU2411637C1 - Precision operational amplifier with low voltage of zero shift - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention may be used as device for amplification of analogue signals, in structure of analogue microchips of various functional purpose (for instance, in precision comparators and operational amplifiers (OA) with low values of zero shift electromotive force). Amplifier comprises input differential cascade (DC) (1), the first (2) and second (3) collector outputs of which are connected to emitters of the first (4) and second (5) output transistors (T), the first current-stabilising dipole (CD) (6), connected to emitter circuit (7) of input DC (1) and emitter of the first (8) auxiliary T, the second CD (9), connected to combined bases of the first T (4) and second T (5), current mirror (10), input of which is connected to collector of the first T (4), and output is connected to collector of the second T (5) and input (11), connected to base of input T (12) of buffer amplifier (13). Base of the first T (8) is connected to emitter of the first T (4), and its collector is connected to bases of the first T (4) and the second T (5), besides, input T (12) of buffer amplifier (13) has the same type of conductivity as the first auxiliary T (8).

EFFECT: reduced absolute value of U_cm and its temperature drift.

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Description

The invention relates to the field of radio engineering and communication and can be used as a device for amplifying analog signals in the structure of analog microcircuits for various functional purposes (for example, in precision comparators and operational amplifiers (op amps) with low values of the emf of zero bias).

In modern microelectronics, cascode differential amplifiers (CDA) are widely used. Among them, a special place is occupied by KDU with servo power supply, providing an increased attenuation coefficient of input common-mode signals and the operation of input transistors at low collector-base voltage in static mode [1-21].

The closest in technical essence to the claimed technical solution is the remote control scheme of figure 1, presented in the patent of the company RCA Corporation USA No. 3614645 figure 2, which is also present in a large number of other patents [1-21].

A significant disadvantage of the well-known KDU of figure 1 is that it has an increased value of the systematic component of the bias voltage zero (U _cm ).

The main objective of the invention is to reduce the absolute value of U _cm and its temperature drift.

This object is achieved in that in the precision operational amplifier of figure 1, containing the input differential stage 1, the first 2 and second 3 collector outputs of which are connected to the emitters of the first 4 and second 5 output transistors, the first current-stabilizing two-terminal 6 connected to the emitter circuit 7 of the input differential cascade 1 and emitter of the first 8 auxiliary transistor, the second 9 current-stabilizing bipolar connected to the combined bases of the first 4 and second 5 output transistors, current mirrors about 10, the input of which is connected to the collector of the first 4 output transistor, and the output is connected to the collector of the second 5 output transistor and input 11, connected to the base of the input transistor 12 of the buffer amplifier 13, new elements and communications are provided - the base of the first 8 auxiliary transistor is connected to the emitter the first 4 output transistor, and its collector is connected to the bases of the first 4 and second 5 output transistors, and the input transistor 12 of the buffer amplifier 13 has the same conductivity type as the first 8 auxiliary trans hist.

The amplifier circuit of the prototype is shown in figure 1. Figure 2 presents a diagram of the inventive device in accordance with claim 1 of the claims. Figure 3 shows a diagram of the CDA corresponding to claim 1 and 2 of the claims. The diagram of figure 4 also corresponds to claims 1 and 2 of the claims. It is used to describe the operation of the claimed device.

In Fig.5, 6 shows a diagram of the differential amplifier of the prototype (Fig.5) and the claimed CDU [Fig.6 (claim 1)] in the computer simulation environment PSpice on models of integrated transistors of FSUE NPP Pulsar.

Figure 7 shows the temperature dependence of the zero bias voltage of the circuits of figures 5 and 6.

On Fig shows a diagram of the CDA, corresponding to claim 2 of the claims, in a computer simulation environment PSpice on models of integrated transistors of FSUE NPP Pulsar.

Figure 9 shows the temperature dependence of the zero bias voltage of the compared circuits of figures 5 and 8.

The precision operational amplifier of FIG. 2 contains an input differential stage 1, the first 2 and second 3 collector outputs of which are connected to the emitters of the first 4 and second 5 output transistors, the first current-stabilizing two-terminal 6 connected to the emitter circuit 7 of the input differential stage 1 and the emitter of the first 8 auxiliary transistor, the second 9 current-stabilizing two-terminal connected to the combined bases of the first 4 and second 5 output transistors, a current mirror 10, the input of which is connected to the collector of the first about 4 output transistors, and the output is connected to the collector of the second 5 output transistor and input 11 connected to the base of the input transistor 12 of the buffer amplifier 13. The base of the first 8 auxiliary transistor is connected to the emitter of the first 4 output transistor, and its collector is connected to the bases of the first 4 and the second 5 output transistors, and the input transistor 12 of the buffer amplifier 13 has the same type of conductivity as the first 8 auxiliary transistor.

In the particular case of the input differential stage 1 (figure 2) is made on transistors 14 and 15.

In the KDU circuit of FIG. 3, the first current-stabilizing two-terminal 6 is connected to the first 8 auxiliary transistor through an additional potential matching circuit 16, made in a particular case on the p-n-p transistor 17.

In the circuit of FIG. 4, an additional emitter follower 16 is also implemented on the transistor 17, and the buffer amplifier 13 is made on the transistor 12, the current-stabilizing two-terminal network 18 and the potential bias circuit 19, by which a predetermined range of variation of the output voltage of the CDD is established.

Consider the factors determining the systematic component of the bias voltage of zero U _cm in the circuit of figure 4, i.e. depending only on the circuitry of the control panel.

If the current of the common emitter circuit 7 of the KDU of Fig. 4 is equal to 2I ₀ , then the collector currents of transistors 14 and 15, the emitter currents of transistors 4 and 5, as well as the input (I input ₁₀ ) and output (I output ₁₀ ) currents of the subcircuit 10 are found by the formulas:

where I _b.p. = I _b.i = I _e.i / β _i is the base current of npn transistors with an emitter current I _e.i = I ₀ ;

β _i is the current gain of the base of npn transistors.

As a result, the current difference in node “A” when it is short-circuited to an equipotential common bus

Substituting (1) - (5) in (6), we find that the difference current in the node "A", which determines U _cm , is close to zero:

As a result, this reduces U _cm , since the differential current I _p in the node “A” creates U _cm , which depends on the steepness of the conversion of the input differential voltage (u _in ) of the CDU into the output current of the node “A”:

where r _e15 = r _e14 are the resistance of the emitter junctions of the input transistors 15 and 14 of the differential stage 1. Therefore, for the circuits of figures 1 to 4

where φ _t = 26 mV is the temperature potential.

In the CDA prototype of FIG. 1, I _p ≠ 0, therefore, the systematic component of U _{cm is} obtained more than an order of magnitude more (U _{cm 1} = 2 mV) than in the claimed circuit (U _cm = 21.7 μV (FIG. 5 , 6)).

Computer simulation of the circuits of Fig.5, 6, 8 confirms (Fig.7, 9) these theoretical conclusions.

Thus, the claimed device has significant advantages in comparison with the prototype in terms of the value of the static error of amplification of DC signals.

Bibliographic list

1. US patent No. 3614645, figure 2.

2. England patent No. 1274672, figure 2.

3. US patent No. 3482177.

4. US Patent No. 3614645.

5. US patent No. 3660773.

6. Patent of England No. 1334759.

7. Patent of Germany No. 1214733.

8. French patent No. 1484340.

9. French patent No. 1584575.

10. Swedish patent 359989.

11. Autost. USSR 970638.

12. US patent No. 3938055.

13. US patent application No. 2007/0069815.

14. US patent No. 5332937, figure 2.

15. Germany patent No. 2039399, figure 4.

16. Autost. USSR 922698.

17. Patent of England No. 1212342, figure 1

18. Patent of Czechoslovakia No. 145527.

19. US patent No. 4151483, Fig.3.

20. US patent No. 4151484, Fig.3.

21. French patent No. 2482177.

Claims (2)

1. A precision operational amplifier with a low zero bias voltage, containing an input differential stage (1), the first (2) and second (3) collector outputs of which are connected to the emitters of the first (4) and second (5) output transistors, the first current-stabilizing two-terminal device ( 6) connected to the emitter circuit (7) of the input differential stage (1) and the emitter of the first (8) auxiliary transistor, the second (9) current-stabilizing two-terminal connected to the combined bases of the first (4) and second (5) output transistors, a current mirror log (10), the input of which is connected to the collector of the first (4) output transistor, and the output is connected to the collector of the second (5) output transistor and input (11) connected to the base of the input transistor (12) of the buffer amplifier (13), characterized in that the base of the first (8) auxiliary transistor is connected to the emitter of the first (4) output transistor, and its collector is connected to the bases of the first (4) and second (5) output transistors, and the input transistor (12) of the buffer amplifier (13) has such the same type of conductivity as the first (8) auxiliary transi side 2. The device according to claim 1, characterized in that the first current-stabilizing two-terminal device (6) is connected to the first (8) auxiliary transistor through an additional potential matching circuit (16).

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