RU2422981C1 - Differential ac amplifier - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: differential amplifier comprises an input differential cascade (1) with the first (2) and the second (3) current outputs, the first (4) and the second (5) current-stabilising dipoles connected between appropriate first (2), second (3) current outputs of input differential cascade (1) and the first (6) bus of supply source, the first (7) and second (8) current mirrors, common emitter outputs of which are connected to the second (9) bus of supply source, the input of the first (7) current mirror is connected to the first (2) current output of input differential cascade (1), and its current output is connected to the first output of the first load dipole (10) and the first output of a device, the input of the second current mirror (8) is connected to the second (3) current output of input differential cascade (1), and its current output is connected to the first output of the second load dipole (11). The second output of the first (10) dipole of a collector load is connected to the first (6) bus of the supply source via the first (12) additional resistor and via the first (13) separating capacitor it is connected to the input of the second (8) current mirror, and the second output of the second (11) dipole of a collector load is connected to the first (6) bus of the supply source via the second (14) additional resistor and via the second (15) separating capacitor is connected to the input of the first (7) current mirror.

EFFECT: increased limit values of amplification ratio values by voltage of a differential amplifier at low-voltage supply and during its operation with alternating signals of HF and SHF ranges.

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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, RF and microwave AC amplifiers, etc.).

In modern microelectronics, differential AC amplifiers (ДУ) with active loads in the form of current mirrors (TK) are widely used, which allow to obtain a high gain. A special place in this class of remote control is occupied by asymmetric [1-3] and symmetric [4] circuits based on the so-called “bent” inclusion of current mirrors, which can be implemented only on n-p-n-transistors, or using low-quality p- np transistors in the structure of current-stabilizing two-terminal devices. In connection with the widespread adoption of SG25VD technology in Russia and other countries of the world SiGe, which does not allow the use of pnp active elements, improving the circuitry of the class of devices under consideration is a fairly urgent task.

The closest in technical essence to the claimed device is a differential amplifier in the device according to the application US 2004/0008085, fig.5.

A significant drawback of the known DE, the architecture of which is also present in other amplification stages [1-3], is that under restrictions on the supply voltage (E _p ) characteristic of SiGe technological processes (E _p ≤2.0 ÷ 2.5 C), its voltage gain (K _y ) is small (K _max = 10 ÷ 20). This is primarily due to restrictions on the resistances of the collector load resistors, which, due to small E _p, cannot be selected as high resistance.

The main objective of the invention is to increase the limit values of the gain in the voltage of the remote control at low voltage power and its operation with alternating signals of the high and microwave ranges.

The problem is solved in that in an alternating current differential amplifier (Fig. 1) containing an input differential stage 1 with first 2 and second 3 current outputs, the first 4 and second 5 current-stabilizing two-terminal devices connected between the corresponding first 2, second 3 current outputs of the input differential cascade 1 and the first 6 bus of the power source, the first 7 and second 8 current mirrors, the common emitter outputs of which are connected to the second 9 bus of the power source, the input of the first 7 current mirror is connected to the first 2 currents m output of the input differential stage 1, and its current output is connected to the first output of the first 10 bipolar load and the first output of the device, the input of the second 8 current mirror is connected to the second 3 current output of the input differential stage 1, and its current output is connected to the first output of the second 11 bipolar load, new elements and connections are provided - the second output of the first 10 bipolar collector load is connected to the first 6 bus power supply through the first 12 additional resistor and through the first 13 section Tel'nykh capacitor connected to the input of the second current mirror 8, and the second terminal of the second 11 two-pole collector load 6 connected to the first power supply bus via a second additional resistor 14 and via the second coupling capacitor 15 connected to the input 7 of the first current mirror.

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.

Figure 4 presents a diagram of the claimed remote control (figure 2) in the computer simulation environment Cadence on models of integrated transistors HJW.

The graph of Fig. 4 characterizes the frequency dependence of the voltage gain (K _y ) of the remote control (Fig. 3) at different values of the capacitance of the separation capacitors C ₁₃ = C ₀ = C ₁₅ = C ₁ = υar.

The differential AC amplifier (Fig. 2) contains an input differential stage 1 with the first 2 and second 3 current outputs, the first 4 and second 5 current-stabilizing two-pole connected between the corresponding first 2, second 3 current outputs of the input differential stage 1 and the first 6 source bus power supply, the first 7 and second 8 current mirrors, the common emitter outputs of which are connected to the second 9 bus of the power supply, the input of the first 7 current mirror is connected to the first 2 current output of the input differential hell 1, and its current output connected to a first terminal of a first two-terminal load 10 and a first output device, the input 8 of the second current mirror coupled to the second current output 3 of the differential input stage 1, and its current output connected to a first terminal of a second two-terminal network 11 load. The second output of the first 10 bipolar collector load is connected to the first 6 bus of the power supply through the first 12 additional resistor and through the first 13 isolation capacitor is connected to the input of the second 8 current mirror, and the second output of the second 11 bipolar collector load is connected to the first 6 bus of the power supply through the second 14 additional resistor and through the second 15 isolation capacitor connected to the input of the first 7 current mirror. In a particular case, the input differential stage 1 is implemented on transistors 16, 17 and a current source 18.

The first 7 current mirror is implemented based on the transistor 19 and the pn junction 20, the second 8 current mirror includes a transistor 21 and the pn junction 22.

The static mode of the remote control (figure 2) is set by the current source 18, as well as the current-stabilizing two-terminal 4 and 5.

Consider the operation of the remote control (figure 2) on alternating current.

The maximum gain factor for the voltage of the remote control (figure 2) for the output "Out.1" with the capacitance of isolation capacitors 13 (C ₁₃ ) and 15 (C ₁₅ ) equal to zero and R10 >> R12, R11 >> R14, is determined by the resistance of the first 10 collector resistors:

where S _1-2 ≈ (r _e16 + r _e17 ) ^-1 is the slope of the amplification of the remote control in the short circuit mode at its output "Out.1", depending on the resistance of the emitter junctions (r _e16 , r _e17 ) of the transistors 16 and 17.

Higher values of K _y in the mid-frequency range, when the influence of the capacitances of the separation capacitors 13 and 15 on K _y can be neglected, are realized in the circuit of FIG. 2 at C ₁₃ = C ₁₅ ≠ 0.

Indeed, the complex transmission coefficient for the voltage of the remote control (figure 2) at the output "Out.1" is determined by the formula:

- комплекс эквивалентного выходного импеданса в цепи первого выхода устройства (узел В);

- комплексная крутизна ДУ в режиме короткого замыкания его первого выхода.Where

- a complex of equivalent output impedance in the circuit of the first output of the device (node B);

- the integrated slope of the remote control in the short circuit mode of its first output.

можно найти по формуле:Equivalent Load Complex

can be found by the formula:

- выходной ток узла «В» в классическом режиме определения выходного сопротивления электронной подсхемы.Where

- the output current of the node "B" in the classical mode of determining the output resistance of the electronic subcircuit.

Moreover

,

,

- комплексы входного и выходного токов первого 7 токового зеркала;

- complexes of input and output currents of the first 7 current mirrors;

,

- комплексы токов через двухполюсники 10 и 11;

,

- complexes of currents through bipolar 10 and 11;

- комплекс импеданса второго 15 разделительного конденсатора;

- impedance complex of the second 15 isolation capacitor;

, r_вх.7 - коэффициент передачи по току первого 7 токового зеркала и его входное сопротивление.

, r _I.7 - current transfer coefficient of the first 7 current mirror and its input resistance.

After transformations of the last formula, taking into account the symmetry of the circuit (u _out.1 = u _out.2 = u _out ) we find that

Therefore, the voltage gain complex of the remote control of FIG. 2

:or at

:

- коэффициент усиления ДУ-прототипа.Where

- gain of the remote control prototype.

Thus, the gain in K _y , which gives the scheme of the remote control of figure 2 in comparison with the prototype of figure 1:

и

:In the mid-frequency region, when the influence of capacitors 13 and 15 on

and

:

From equation (8), a number of important conclusions follow:

1. Firstly, the K efficiency of _the proposed circuitry of FIG. 2 depends on the parameters: K _i7 , R ₁₀ / R ₁₁ , r _{input 7} / R ₁₄ .

2. Secondly, to obtain the maximum gain in K _y you must choose:

.In this case

.

The graph of Fig. 4, obtained as a result of modeling the circuit of Fig. 3 in the Cadence environment, shows that the gain in K _y in the mid-frequency range, in which the influence of capacitances of isolation capacitors 13 and 15 (C ₁₅ = C ₁₃ = C ₁ = C ₀ ) can be neglected, reaches 16 dB (i.e., almost ten times).

The inventive circuit is especially promising for use in microelectronic microwave devices implemented by the SG25VD process technology being introduced in Russia, which does not allow the use of pnp transistors.

Information sources

1. US patent No. 4.418.290 fig.10.

2. US patent No. 5.376.897.

3. US patent No. 4.366.445.

4. US Patent Application 2004/0008085.

Claims (1)

A differential AC amplifier containing an input differential stage (1) with first (2) and second (3) current outputs, the first (4) and second (5) current-stabilizing two-pole connected between the corresponding first (2), second (3) current the outputs of the input differential stage (1) and the first (6) bus of the power source, the first (7) and second (8) current mirrors, the common emitter outputs of which are connected to the second (9) bus of the power source, the input of the first (7) current mirror is connected with first (2) current output of input differential cascade (1), and its current output is connected to the first output of the first (10) two-terminal load and the first output of the device, the input of the second (8) current mirror is connected to the second (3) current output of the input differential stage (1), and its current the output is connected to the first terminal of the second (11) two-terminal load, characterized in that the second terminal of the first (10) two-terminal collector load is connected to the first (6) bus of the power source through the first (12) additional resistor and through the first (13) isolation capacitor is connected from the entrance m of the second (8) current mirror, and the second output of the second (11) collector load two-port terminal is connected to the first (6) bus of the power supply through the second (14) additional resistor and through the second (15) isolation capacitor is connected to the input of the first (7) current mirrors.

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