RU2399151C1 - Differential amplifier - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention can be used as a device for amplifying analogue signals, in analogue microcircuits for various functional purposes (e.g. in comparators and precision operational amplifiers with small zero offset emf values). The differential amplifier has a first (1) and a second (2) input transistor, between emitters of which a local negative feedback resistor (3) is connected, a first (4) current stabilising two-terminal element connected to the emitter of the first (1) input transistor, a second (5) current stabilising two-terminal element connected to the emitter of the second (2) input transistor, a third (6) current stabilising two-terminal element connected to the collector of the first (1) input transistor and the emitter of the first (7) output transistor, whose base is connected to the emitter of the first (1) input transistor, a fourth (8) current stabilising two-terminal element (8) connected to the collector of the second (2) input transistor and the emitter of the second (9) output transistor, a current mirror (10) whose input is connected to the collector of the first (7) output transistor, while the output is connected to the collector of the second (9) output transistor and the base of the input transistor (11) of the buffer amplifier (12). The base of the second (9) output transistor is connected to the base of the first (7) output transistor. Conductivity type of the input transistor (11) of the buffer amplifier (12) is the same as that of the first (7) and second (9) output transistors.

EFFECT: low absolute value zero offset emf U_off 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 comparators and precision operational amplifiers (op amps) with low values of the emf of zero bias).

In modern analog microelectronics, one can distinguish a subclass of differential amplifiers based on the so-called “bent” cascode with tracking power [1-12]. They are among the most broadband. The present invention relates to this type of remote control.

The closest in essence to the claimed technical solution is the control scheme of figure 1, presented in the Development Catalog of the Russian-Belarusian Center for Analog Microcircuitry. - Mines: Publishing House of SRUES, 2006 (p. 65), which is also present in a large number of patents of leading microelectronic companies, for example, [1-12].

A significant drawback of the known DE of FIG. 1 is that it has an increased value of the systematic component of the zero bias voltage (U _cm ), which depends on the properties of its architecture.

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

The problem is achieved in that in the differential amplifier of Fig. 1, containing the first 1 and second 2 input transistors, between the emitters of which a resistor 3 of local negative feedback is connected, the first 4 is a stabilizing two-terminal device connected to an emitter of the first 1 input transistor, and the second 5 is a current stabilizing two-terminal device connected to the emitter of the second 2 input transistor, the third 6 current-stabilizing two-terminal connected to the collector of the first 1 input transistor and the emitter of the first 7 output trans a resistor, the base of which is connected to the emitter of the first 1 input transistor, the fourth 8 is a current-stabilizing two-terminal connected to the collector of the second 2 input transistor and the emitter of the second 9 output transistor, a current mirror 10, the input of which is connected to the collector of the first 7 output transistor, and the output is connected to the collector the second 9 output transistor and the base of the input transistor 11 of the buffer amplifier 12, new communications are provided - the base of the second 9 output transistor is connected to the base of the first 7 output transistor, moreover, the type of conductivity of the input transistor 11 of the buffer amplifier 12 coincides with the type of conductivity of the first 7 and second 9 output transistors.

The amplifier circuit of the prototype is shown in figure 1. Figure 2 presents a diagram of the inventive device in accordance with the claims.

In Fig.3 and Fig.4 shows a diagram of the differential amplifier of the prototype (Fig.3) and the claimed remote control (Fig.4) in the environment of computer simulation PSpice on models of integrated transistors of FSUE NPP Pulsar.

Figure 5 shows the temperature dependence of the zero bias voltage of the circuits of figure 3, figure 4.

The differential amplifier of figure 2 contains the first 1 and second 2 input transistors, between the emitters of which a local negative feedback resistor 3 is included, the first 4 current-stabilizing two-terminal connected to the emitter of the first 1 input transistor, the second 5 current-stabilizing two-terminal connected to the emitter of the second 2 input transistor , the third 6 current-stabilizing two-terminal connected to the collector of the first 1 input transistor and the emitter of the first 7 output transistor, the base of which is connected to the emitter the first 1 input transistor, the fourth 8 current-stabilizing two-terminal connected to the collector of the second 2 input transistor and the emitter of the second 9 output transistor, a current mirror 10, the input of which is connected to the collector of the first 7 output transistor, and the output is connected to the collector of the second 9 output transistor and the base of the input the transistor 11 of the buffer amplifier 12. The base of the second 9 output transistor is connected to the base of the first 7 of the output transistor, the conductivity type of the input transistor 11 of the buffer amplifier 12 with drops from the conduction type of the first 7 and second output transistors 9.

Consider the factors that determine the systematic component of the bias voltage of zero U _cm in the circuit of figure 2, i.e. depending on the circuitry of the remote control.

If the currents of the two-terminal circuits 4 and 5 are equal to the value I ₀ , and I ₆ = 2I ₀ = I ₈ , then the collector currents of the transistors 1 and 2:

where I _b.i = I _e.i / β _i is the base current of npn transistors (I _b.p ) and pnp transistors (I _b.n ) at an emitter current I _e.i = I ₀ ;

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

Therefore, at a unit current transfer coefficient of the current mirror 10 (K _i = 1), the emitter and collector currents of the transistors 7 and 9, as well as the input (I input ₁₀ ) and output (I output ₁₀ ) currents of the current mirror 10:

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

where I _{input 12} = 2I _b.n is the base current pnp of the transistor 11 of the buffer amplifier 12.

Substituting (1) ÷ (6) in (7), we find that the difference current determining U _cm

Thus, in the inventive device, when condition (8) is fulfilled, the systematic component U _cm decreases due to the final value of β transistors and its radiation (or temperature) dependence. As a result, this reduces U _cm , since the difference current I _p in the node “A” creates U _cm , depending on the steepness S of the conversion of the input differential voltage u _{in the} remote control into the output current of the node “A”:

where r _e1 = r _e2 - resistance of the emitter junctions of the input transistors 1 and 2,

R ₃ - resistance of a two-terminal 3.

Therefore, for the circuit of FIG. 2

where φ _T = 26 mV is the temperature potential.

In the remote control prototype I _p = -2I _b.n , therefore, here the systematic component U _cm is two orders of magnitude greater (U _cm = 10.5 mV) than in the claimed circuit (U _cm = 65 μV).

Computer simulation of the schemes of figure 3, figure 4 confirms (figure 5) 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.

Information sources

1. Czech patent No. 145526.

2. Czech patent No. 145528.

3. US patent No. 4151482.

4. French patent No. 2066287.

5. England patent No. 1276375.

6. French patent No. 2023 887.

7. US Patent No. 3825774 fig. 8.

8. A. St. USSR No. 813692.

9. US patent No. 4151484 fig. 4.

10. German patent No. 2039399.

11. Swedish patent No. 365675.

12. US Patent No. 4,406,990 fig. 4.

Claims (1)

A differential amplifier containing the first (1) and second (2) input transistors between which emitters includes a local negative feedback resistor (3), the first (4) current-stabilizing two-terminal connected to the emitter of the first (1) input transistor, and the second (5) a current-stabilizing two-terminal connected to the emitter of the second (2) input transistor, a third (6) current-stabilizing two-terminal connected to the collector of the first (1) input transistor and the emitter of the first (7) output transistor, the base of which is connected to the em the ytter of the first (1) input transistor, the fourth (8) current-stabilizing two-terminal connected to the collector of the second (2) input transistor and the emitter of the second (9) output transistor, a current mirror (10), the input of which is connected to the collector of the first (7) output transistor and the output is connected to the collector of the second (9) output transistor and the base of the input transistor (11) of the buffer amplifier (12), characterized in that the base of the second (9) output transistor is connected to the base of the first (7) output transistor, and the input conductivity type the first transistor (11) of the buffer amplifier (12) coincides with the first conductivity type (7) and second (9) output transistors.

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