RU2421896C1 - Differential amplifier with increased amplification coefficient as to voltage - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: differential amplifier includes the first (1) and the second (2) input transistors (T) between the emitters of which feedback bipole (3) is connected, the first (4) current-stabilising bipole connected between emitter of the first (1) input T and the first (5) power source (PS); the second (6) current-stabilising bipole connected between emitter of the second (2) input T and the first (5) PS; the first (7) resistor of collector load connected through the first output to the first (8) output of the device and collector of the first (1) input T, the second (9) resistor of collector load connected through the first output to the second (10) output of the device and collector of the second (2) input T; the second (11) PS. To the diagram there introduced is the first (12) and the second (13) current mirrors the common emitter outputs of which are connected to the second (11) PS; input of the first (12) current mirror is connected to the second output of the first (7) resistor of collector load; input of the second (13) current mirror is connected to the second output of the second (9) resistor of collector load; output of the first (12) current mirror is connected to emitter of the second (2) input T, and output of the second (13) current mirror is connected to emitter of the first (1) input T. ^ EFFECT: increasing amplification coefficient as to voltage when using relatively low-ohmic resistors of collector load in conditions of processing limits of SiGe-technology for power supply voltages. ^ 6 dwg

Description

The invention relates to the field of radio engineering and communications and can be used as a device for amplifying analog signals in the structure of analog microcircuits of various functional purposes (for example, SiGe-operational amplifiers (op amps), comparators, continuous voltage stabilizers, etc.).

In modern microelectronics, the simplest differential amplifiers (ДУ) are widely used (Fig. 1) with local negative feedback, which are used as elements of emitter-coupled logic, communication line drivers, elementary operational amplifiers with differential output, filters based on them, and microwave amplifiers etc. The voltage gain (K _y ) of such remote controls depends primarily on the resistances of the resistors in the collector circuit of the input transistors and the local negative feedback resistor.

When using SiGe technological processes, the power supply voltage of the remote control must not exceed 1.5 ÷ 2.5 V, which imposes significant restrictions on the resistance of collector resistors, which should not exceed units of kilo-ohms.

The closest in technical essence to the claimed device is a remote control (figure 1), discussed in US patent No. 4511852 figure 3. It contains the first 1 and second 2 input transistors, between the emitters of which there is a feedback 3-pole, the first 4 current-stabilizing two-terminal connected between the emitter of the first 1 input transistor and the first 5 power supply, the second 6 current-stabilizing two-pole connected between the emitter of the second 2 input transistor and the first 5 power supply, the first 7 collector load resistor connected to the first output with the first 8 output of the device and the collector of the first 1 input transistor, the second 9 collector resistor the load associated with the first output with the second 10 output of the device and the collector of the second 2 input transistor, the second 11 power supply.

A significant drawback of the known DE of FIG. 1, which is also present in patents [2-15], is that when using a collector load of 7 and 9 with a resistance of 1 ÷ 2 kOhm, its voltage gain (K _y ) is small:

where R ₉ is the resistance of the collector load resistor 9;

R ₃ - differential resistance of the two-terminal feedback 3;

r _ei << R ₃ is the resistance of the emitter junction of the i-th transistor. For example, when R ₉ = 1 kOhm and R ₃ = 500 Ohm, the gain of the DU prototype K _uprot ≈2. In most cases, this is not enough.

The main objective of the invention is to increase the voltage gain when using relatively low resistance resistors load collectors (for example, R ₉ = R ₇ = 14 ÷ 2 kOhm) under the technological restrictions of SiGe technology for supply voltage (± 1.9 ÷ 2 B )

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 feedback 2-pole 3 is connected, the first 4 current-stabilizing two-terminal, connected between the emitter of the first 1 input transistor and the first 5 power supply, the second 6 current-stabilizing bipolar connected between the emitter of the second 2 input transistor and the first 5 power source, the first 7 collector load resistor connected to the first output with the first 8 output properties and collector of the first 1 input transistor, second 9 collector load resistor, connected by the first output to the second 10 output of the device and the collector of the second 2 input transistor, second 11 power supply, new elements and communications are provided - the first 12 and second 13 current mirrors are introduced into the circuit the common emitter outputs of which are connected to the second 11 power source, the input of the first 12 current mirror is connected to the second output of the first 7 collector load resistor, the input of the second 13 current mirror is connected to the second pin th second collector load resistor 9, the output of the first current mirror 12 is connected to the emitter of the second input transistor 2, and the output of the second current mirror 13 is connected to the emitter of the first input transistor 1.

In Fig.1 shows a diagram of the remote control prototype.

A diagram of the inventive device corresponding to the claims is shown in figure 2.

In Fig.3 shows a diagram of the remote control of Fig.1 in the computer simulation environment of Cadence on models of integrated transistors of FSUE NLP Pulsar, and in Fig.4 - of the inventive device of Fig.2.

The drawing of figure 5 shows the frequency dependence of the gain on the voltage of the compared remote control of figure 3 and figure 4. These graphs show that, despite the use of a low-impedance collector load (R ₆₀ = R ₆₁ = 1 kOhm) and the introduction of local negative feedback in the form of a resistor R ₅₉ = R ₃ (626 Ohms), the voltage gain of the remote control (Fig. 4 ) increases by 75 dB, i.e. more than three orders of magnitude in comparison with K _y remote control of the prototype of figure 3. This is an important advantage of the proposed remote control during its implementation in the framework of promising SiGe technological processes.

In Fig.6 shows graphs of the dependence of the gain of the compared circuits of Fig.3, Fig.4 from the resistances of the bipolar local negative feedback 3 (R ₃ = R ₅₉ = R ₆₃ in the circuits of Fig.3 and Fig.4). From these graphs it follows that the voltage gain in the claimed circuit is always greater than the gain of the remote control prototype, and there is some optimal value of the resistance of the resistor 3, at which K _y takes an extremely high value.

The differential amplifier with a high voltage gain of FIG. 2 contains the first 1 and second 2 input transistors, between the emitters of which a feedback 3-pole is included, the first 4 current-stabilizing two-terminal connected between the emitter of the first 1 input transistor and the first 5 power supply, the second 6 current-stabilizing a two-terminal device connected between the emitter of the second 2 input transistor and the first 5 power supply, the first 7 collector load resistor connected to the first output with the first 8 output m of the device and the collector of the first 1 input transistor, the second 9 collector load resistor connected to the first output with the second 10 output of the device and the collector of the second 2 input transistor, the second 11 power supply. The first 12 and second 13 current mirrors are introduced into the circuit, the common emitter outputs of which are connected to the second 11 power source, the input of the first 12 current mirrors is connected to the second output of the first 7 collector resistor, the input of the second 13 current mirrors is connected to the second output of the second 9 collector resistor load, the output of the first 12 current mirror is connected to the emitter of the second 2 input transistor, and the output of the second 13 current mirror is connected to the emitter of the first 1 input transistor.

Consider the operation of the proposed device of figure 2.

The static mode of the remote control of FIG. 2 is set by bipolar 4 and 6. If we neglect the output impedance of transistors 1 and 2, then the voltage gain of the remote control of FIG. 1 from the outputs of Outputs 2 and Output 1 is determined by the formulas:

where R _n.Eq.2 , R _n.Eq.1 - equivalent resistance in the nodes "Out.2" and "Out.1", respectively.

Moreover, R _{N.E. 2} and R _{N.E. 1} as output impedances while changing u _{output 2} and u _{output 1} can be found from the expression:

Where

In the latest formulas:

K _il2 ≤1 - current gain of the first 12 current mirror;

u _output = u _output 1 = u _{output 2} - the amplitude of the output antiphase voltage remote control.

Thus, the voltage gain of the remote control of figure 2:

where K _d1 <1 is the division ratio of the output current i _pt.2 between the emitter of the transistor 1 and the two-terminal 13:

Moreover, α ₂ = 0.98-0.99 is the current gain of the emitter of transistor VT1 in a circuit with a common base.

Therefore, when R ₉ = R ₇ gain in K _y in the scheme of figure 2

In practical schemes, K _i12 and K _{d1 are} always less than one (K _i12 = 0.9 ÷ 0.99, K _d1 = 0.98 ÷ 0.99). However, with R9 = R7, the gain in _K.sub.z is significant (Fig. 5, Fig. 6).

The numerical values of R ₃ affect K _y in a complex way. If R ₃ = 0, then _K.s. = _K.s. For large R ₃ >> 3, the transfer of currents i _pt.12 and i _pt.13 to the emitters of transistors 1 and 2 improves, which allows to obtain in the limit

However, when you consider that the transistor 2 has some output resistance

where μ ₂ = 10 ^-3 ÷ 10 ^-4 is the internal feedback coefficient of the second 2 transistor inputs, then in the ideal case when K _i.12 = l, α ₂ = 1, the gain of the remote control of Fig. 2 cannot exceed the values:

Thus, the proposed device has significant advantages in gain compared with the prototype.

Literature

1. M. Herpy. Analog integrated circuits. M .: Radio and communications, 1983 - S.366, Fig. 8.11.

2. Patent EP 0058448, H03f 3/45.

3. Auth. testimonial. USSR No. 853776, G03g 3/36.

4. Auth. testimonial. USSR No. 488317, H03h 7/44.

5. Greben A.B. Designing analog integrated circuits. - M .: World - S.147, Fig. 7-5.

6. US patent No. 4146844, cl. 330-149.

7. Japanese Patent 53-33232 98 (5) A 333.

8. England patent No. 1429793 H03f 1/34.

9. Patent of England No. 1572079, H3T.

10. US patent No. 4511852.

11. US patent application No. 2002/0053935.

12. US patent No. 6456142, Fig.8.

13. US patent No. 5184088, figure 2.

14. US patent No. 5821810.

15. UK patent No. 2318470.

Claims (1)

A differential amplifier with a high voltage gain, containing the first (1) and second (2) input transistors, between the emitters of which a two-terminal feedback (3) is included, the first (4) current-stabilizing two-terminal, connected between the emitter of the first (1) input transistor and the first (5) power supply, the second (6) current-stabilizing two-pole connected between the emitter of the second (2) input transistor and the first (5) power supply, the first (7) collector load resistor connected to the first output from the first (8) the output of the device and the collector of the first (1) input transistor, the second (9) collector load resistor connected to the first output with the second (10) output of the device and the collector of the second (2) input transistor, the second (11) power source, characterized in that the first (12) and second (13) current mirrors are introduced into the circuit, the common emitter outputs of which are connected to the second (11) power source, the input of the first (12) current mirror is connected to the second output of the first (7) collector load resistor, input the second (13) current mirror is connected to orym second terminal (9) of the collector load resistor, a first output (12) of the current mirror is connected to the emitter of the second (2) input transistor and the second output (13) of the current mirror is connected to the emitter of the first (1) of the input transistor.

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