RU2411638C1 - Differential operational amplifier with low voltage of zero shift - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention may be used as device for amplification of analog signals, in structure of analog microchips of various functional purpose (for instance, in comparators and precision operational amplifiers (OA) with low values of zero shift electromotive force). Differential operational amplifier with low voltage of zero shift comprises the first (1) and second (2) input transistors, between emitters of which a resistor (3) of local negative feedback is connected, the first current-stabilising dipole (CD) (4), connected to emitter of the first T (1), the second CD (5), current mirror (6), input of which is connected to collector of the first T (1), and output is connected to collector of the second T (2) and base of input T (7) of output emitter repeater, the third CD (8), related to output of device (9) and emitter T (7). Circuit includes auxiliary T (10), collector of which is connected to emitter of the second T (2), and emitter is connected to the second CD (5), and base is connected to circuit of potentials shift (11).

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

4 cl, 11 dwg

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 small values of the emf of zero bias).

In modern electronic equipment, differential amplifiers (DU) with significant different parameters are used.

A special place is occupied by differential amplifiers (DU) with local negative feedback, which is provided by a resistor connected between the emitters of the input transistors of the DU. Such remote controls are used in high-speed operational amplifiers and are characterized by an extended range of linear operation. The present invention relates to this type of remote control.

The closest in technical essence to the claimed technical solution is the classical scheme of the remote control of FIG. 1, presented in US patent No. 5365191, fig.9, which is also present in a large number of other patents having controllable current mirrors as a load circuit of input transistors [1- 7].

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 local negative feedback resistor 3 is connected, the first current-stabilizing two-terminal 4 connected to the emitter of the first 1 input transistor, the second current-stabilizing two-terminal 5 , a current mirror 6, the input of which is connected to the collector of the first 1 input transistor, and the output is connected to the collector of the second 2 input transistor and the base of the input transistor 7 of the output emitter a second repeater, a third current-stabilizing two-terminal device 8, connected to the output of the device 9 and the emitter of the transistor 7 of the output emitter repeater, new elements and communications are provided - an auxiliary transistor 10 is inserted into the circuit, the collector of which is connected to the emitter of the second 2 input transistor, the emitter is connected to the second 5 current-stabilizing bipolar, and the base is connected to a potential bias circuit 11.

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

The scheme of figure 3 corresponds to claim 1 and claim 2 of the claims. In the drawings of figures 4, 5 show the options for constructing a bias circuit of potentials 11 corresponding to claim 3 (figure 4) and claim 4 (figure 5) of the claims.

In the drawing of Fig.6 shows a diagram of a differential amplifier - a prototype, and in the drawing of Fig.7 - of the claimed remote control in a computer simulation environment PSpice on models of integrated transistors of FSUE NPP Pulsar.

The drawing of Fig.8 shows the temperature dependence of the zero bias voltage of the circuits of Fig.6, 7.

The drawing of Fig. 9 shows a diagram of Fig. 1 in a computer simulation environment PSpice on models of integrated transistors of the Federal State Unitary Enterprise NPP "Pulsar", which is compared with the circuit of the claimed control unit of Fig. 10, corresponding to claim 3 of the claims.

The drawing of Fig.11 shows the dependence of U _cm = f (t °) schemes of Figures 9 and 10.

The differential amplifier of Fig. 2 contains a first 1 and a second 2 input transistors, between the emitters of which a local negative feedback resistor 3 is included, a first current-stabilizing two-terminal 4 connected to an emitter of the first 1 input transistor, a second current-stabilizing two-terminal 5, a current mirror 6, the input of which is connected with the collector of the first 1 input transistor, and the output is connected to the collector of the second 2 input transistor and the base of the input transistor 7 of the output emitter follower, the third is current-stabilizing the first two-terminal 8 connected to the output of the device 9 and the emitter of the transistor 7 of the output emitter follower. An auxiliary transistor 10 is introduced into the circuit, the collector of which is connected to the emitter of the second 2 input transistor, the emitter is connected to the second 5 current-stabilizing bipolar, and the base is connected to the potential bias circuit 11.

In a particular case, the bias circuit of potentials 12 and 13, implemented on the basis of various two-terminal devices, is introduced into the circuit of Fig. 2.

In the drawing of FIG. 3, having a practical implementation of two-terminal devices 4, 5 and 8 based on auxiliary transistors 14, 15, 16 and resistors 17, 18, 19, in accordance with claim 2, a thermo-radiation compensation transistor 20 is introduced. the mode of transistors 14, 15, 16 along the base circuit is set by the auxiliary power source 21.

In the drawing of FIG. 4, in accordance with claim 3, the potential bias circuit 11 is implemented based on the first additional transistor 22, and the base of the first additional transistor 22 is connected to the emitter of the second 2 input transistor, and its emitter is the output of the potential bias circuit 11 and connected to the base of the auxiliary transistor 10.

In the drawing of FIG. 5, in accordance with claim 4, the potential bias circuit 11 is implemented based on the second 23 additional transistor, the base of the second 23 additional transistor connected to the base of the second 2 input transistor, and the emitter is the output of the potential bias circuit 11 and connected to the base of the auxiliary transistor 10.

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 two-terminal 4, 5 and 8 are equal to 10, then the currents of the collectors of transistors 1, 10 and 2:

where I _bp = I _e.i / β _i is the base current of npn transistors 1, 2, 10, 7 at an emitter current I _e.i = I ₀ ;

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

Input I input ₆ and output I output ₆ currents of the current mirror 6

where K _i = 1 - modulus of the current transfer coefficient of the current mirror 6.

As a result, the current difference in the node "A" when it is shorted to the equipotential common bus and the current of the two-terminal 8 I ₈ = I ₀ is close to zero:

where I _b.7 = I _b.r - base current npn of the transistor 7 of the output emitter follower.

Thus, in the inventive device, when condition (6) is satisfied, the systematic component U _cm decreases. As a result, this reduces U _cm , since the difference current I _p in the node “A” creates U _cm , which depends 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 ≠ 0, therefore, here the systematic component U _{cm is} obtained more than an order of magnitude more than in the claimed scheme (Fig. 8, 11).

Computer simulation of the circuits of Fig.6, 7, 9, 10 confirms (Fig.8, 11) these theoretical conclusions.

To minimize U _cm at elevated temperatures (t °> 80 ° C), a transistor 20 is provided in the circuit of FIG. 3, which is in the closed state. However, the current through its pn junction to the substrate, which increases significantly at high temperatures (or during radiation exposure), compensates for the corresponding current to the substrate through the pn junction of transistor 10. This significantly reduces the derivative dU _cm / dT at t °> 80 ° C (Fig. 8).

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. 4636743, fig. 1.

2. U.S. Patent No. 5,828,242, fig. 5.

3. US Patent No. 5365191, fig. 9.

4. US patent No. 4636744.

5. US Patent No. 6,281,752, fig. 5a.

6. US patent No. 4783637.

7. US patent No. 4757275, fig.2.

Claims (4)

1. A differential operational amplifier with a low zero bias voltage, containing the first (1) and second (2) input transistors, between the emitters of which a local negative feedback resistor (3) is connected, the first current-stabilizing two-terminal device (4) connected to the emitter of the first (1) ) an input transistor, a second current-stabilizing two-terminal device (5), a current mirror (6), the input of which is connected to the collector of the first (1) input transistor, and the output is connected to the collector of the second (2) input transistor and the base of the input transistor (7) one emitter follower, the third current-stabilizing two-terminal (8) connected to the output of the device (9) and the emitter of the transistor (7) of the output emitter follower, characterized in that an auxiliary transistor (10) is inserted into the circuit, the collector of which is connected to the emitter of the second (2) of the input transistor, the emitter is connected to the second (5) current-stabilizing bipolar, and the base is connected to the potential bias circuit (11). 2. The device according to claim 1, characterized in that a thermo-radiation compensation transistor (20) is introduced into the circuit, the collector of which is connected to the emitter of the first (1) input transistor, and the combined emitter and base are connected to the potential bias circuit (11). 3. The device according to claim 1, characterized in that the potential bias circuit (11) is implemented based on the first additional transistor (22), and the base of the first additional transistor (22) is connected to the emitter of the second (2) input transistor, and its emitter is the output of the potential bias circuit (11) and is connected to the base of the auxiliary transistor (10). 4. The device according to claim 1, characterized in that the potential bias circuit (11) is based on the second (23) additional transistor, the base of the second (23) additional transistor connected to the base of the second (2) input transistor, and the emitter is the output potential bias circuit (11) and is connected to the base of the auxiliary transistor (10).

Images