RU2389130C1 - Cascode differential amplifier with controlled amplification - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention may be used in devices of automatic adjustment of amplification, phase detectors and modulators, and also in systems of phase self-tuning and multiplication of frequency or as amplifier, voltage transfer coefficient of which depends on the level of control signal. Controlled amplifier is the basic unit of up-to-date systems for receiving and processing of signals from HF and SHF ranges, analog computer and metering equipment. Cascode differential amplifier (CDA) with controlled amplification comprises the first (1) and second (2) input transistors, emitters of which are connected to source of reference current (3). The first (4) and second (5) output composite transistors, main emitters of which (6, 7) are connected to according collectors of the first (1) and second (2) input transistors, collectors are joined by load circuit (8), and bases are connected to source of shift voltage source (9). Circuit includes additional transistor (10), emitter of which is connected to additional source of reference current (11) and via additional resistor (12) is connected to combined emitters of the first (1) and second (2) input transistors. Base is connected to control input (13) of CDA with controlled amplification, besides as the first (3) and second (4) of output composite transistors, composite transistors are used with the main (6, 7) and additional (14, 15) emitters, which are combined to each other and joined to collector of additional transistor (10).

EFFECT: reduced supply voltage, expansion of functional possibilities of amplifier as mixer.

5 cl, 13 dwg

Description

The present invention relates to the field of radio engineering and communication and can be used in devices for automatic gain control, phase detectors and modulators, in systems of phase locked loop and frequency multiplication, or as an amplifier, the voltage transfer coefficient of which depends on the level of the control signal. The controlled amplifier is the basic unit of modern systems for receiving and processing signals of the high-frequency and microwave ranges, analog computing and measuring equipment.

In modern high-frequency and microwave microcircuitry, cascode differential amplifiers (CDA) are widely used, which, due to weak internal feedback, are among the most high-frequency ones. All known KDUs can be divided into two large subclasses - classical KDUs with the same type of transistors [1-15], and the so-called “kinked” cascodes, in which the output transistors have (in comparison with the input transistors) a different type of conductivity [16-55] .

The closest prototype (figure 1) of the inventive device is a CDA described in the patent of General Electric (USA) No. 3.482.177 (figure 5). It contains the first 1 and second 2 input transistors, the emitters of which are connected to the reference current source 3, the first 4 and second 5 output composite transistors, the main emitters of which 6 and 7 are connected to the corresponding collectors of the first 1 and second 2 input transistors, the collectors are connected by a circuit load 8, and the base is connected to a bias voltage source 9.

It should also be noted that other modifications of KDU with other options for constructing output composite transistors 3 and 4 are known in microcircuitry (US patent No. 5.185.582, author certificate of the USSR No. 1385255, England patent No. 1.520.085, class H3T.

A significant drawback of the well-known KDU is that it does not have a special input “U” for electronic control of the voltage gain. This significantly narrows the scope of its use, does not allow implementing adaptive functional units of systems on a chip, for example, microwave operational amplifiers, in which the loop gain varies according to a given algorithm depending on the properties of the signal sources and feedback circuits (see, for example, RF patent No. 2307393 "Method for controlling the gain of a decision amplifier with deep negative feedback").

The main objective of the invention is to create conditions for electronic control of the gain of voltage KDU. Realization of this goal allows us to perform not only broadband RF and microwave amplifiers with adjustable parameters on the basis of the claimed device, but to create more complex functional units based on it, for example, analog signal multipliers according to the SG25H2 manufacturing process.

The first additional goal is the creation of a KDU architecture with a low supply voltage and electronic control of its voltage gain, as well as providing the possibility of practical implementation of devices using SG25H2 technology (operating voltage for npn transistors U _p = 1.9 V, pn- p transistors U _n = 2.8 V).

An additional goal is the implementation on the basis of the well-known KDU functions of an analog mixer and / or an analog multiplier of two voltages.

The goals are achieved in that in the cascode differential amplifier (figure 2), containing the first 1 and second 2 input transistors, the emitters of which are connected to a reference current source 3, the first 4 and second 5 output composite transistors, the main emitters of which 6 and 7 are connected with the corresponding collectors of the first 1 and second 2 input transistors, the collectors are connected by a load circuit 8, and the bases are connected to a bias voltage source 9, new elements and connections are provided - an additional transistor 10, an emitter of it is connected to an additional source of reference current 11 and through an additional resistor 12 is connected to the combined emitters of the first 1 and second 2 input transistors, the base is connected to the control input 13 of the cascode differential amplifier with controlled amplification, and as the first 3 and second

4 output composite transistors use composite transistors with the main 6, 7 and additional 14, 15 emitters, which are combined with each other and connected to the collector of the additional transistor 10.

The amplifier circuit of the prototype is presented in figure 1. Figure 2 shows the inventive device in accordance with claim 1 of the claims. In this scheme, the output composite transistors 4 and 5 are made in accordance with paragraph 3 of the claims.

Figure 3 also shows the inventive device in accordance with claim 1 of the claims. However, in this circuit, the output composite transistors 4 and 5 are made in accordance with claim 2.

Figure 4 presents the options for constructing output composite transistors 4 and 5 in accordance with paragraph 2 of the claims.

Figure 5 presents the options for constructing output composite transistors 4 and 5 in accordance with claim 3 of the claims.

Figure 6 shows a diagram of the inventive device in accordance with paragraph 4 of the claims.

Figure 7 presents a diagram of the inventive device in accordance with paragraph 5 of the claims.

On Fig is an example of the use of the inventive controlled amplifier as part of an analog voltage multiplier U _x and U _y .

In Fig.9 shows a diagram of the inventive device (Fig.7) in the computer simulation environment PSpice on models of integrated transistors of FSUE NPP Pulsar.

The results of computer simulation of the circuit (Fig.9) are presented in Fig.10-13:

- the dependence of the gain on the voltage K _u from the frequency f at different values of the control voltage U _y = + 400 mV ÷ -300 mV (figure 10);

- the dependence of the gain on the voltage K _u from the voltage at the control input U _y when the resistance of the resistor R ₁ = 100 Ohms (Fig.11);

- the dependence of the gain on the voltage K _u from the voltage at the control input U _y when the resistance of the resistor R ₁ = 500 Ohms (Fig);

- the dependence of the output phase-voltage of the KDU on the voltage at the directing input U _y with the resistance of the resistor R ₁ = 500 Ohms (Fig.13).

The cascode differential amplifier (Fig. 2) contains the first 1 and second 2 input transistors, the emitters of which are connected to the reference current source 3, the first 4 and second 5 output transistors, the main emitters of which 6 and 7 are connected to the corresponding collectors of the first 1 and second 2 input transistors, collectors are connected by a load circuit 8, and the bases are connected to a bias voltage source 9. An additional transistor 10 is introduced into the circuit, the emitter of which is connected to an additional reference current source 11 and through an additional resistor 12 is connected to the combined emitters of the first 1 and second 2 input transistors, the base is connected to the control input 13 of the cascode differential amplifier with controlled amplification, and composite transistors with main 6, 7 and additional 14 are used as the first 3 and second 4 output composite transistors , 15 emitters, which are combined with each other and connected to the collector of an additional transistor 10.

In the circuit (Fig. 4), in accordance with claim 2, each first 3 and second 4 output composite transistor contains a two-emitter transistor 18, the first emitter of the two-emitter transistor being the main emitter 6, 7 of the output composite transistor, and the second emitter as an additional emitter 14 (15) output composite transistor.

In the circuit (Fig. 5), in accordance with claim 3, each first 3 and second 4 output composite transistor contains an auxiliary transistor 19, the emitter of which is the main emitter 6 (7) of the output composite transistor, and an additional emitter 14 (15) of the output the composite transistor is connected to the emitter of the auxiliary transistor 19 through the auxiliary resistor 20.

In the circuit (Fig. 6), in accordance with claim 4, the conductivity of the first 3 and second 4 output composite transistors is opposite to the conductivity of the first 1 and second 2 input transistors, with the main 6 (7) and the combined additional 14 (15) emitters of the output composite transistors are connected respectively with the first 21, second 22 and third 23 auxiliary sources of reference current.

In the circuit (Fig. 7), in accordance with claim 5, the conductivity of the first 3 and second 4 output composite transistors is opposite to the conductivity of the first 1 and second 2 input transistors, the main 6, 7 emitters of the output composite transistors associated with the fourth 24 and fifth 25 auxiliary sources of reference current.

Consider the operation of the claimed device (figure 3).

In static mode, at zero control voltage (u _y = 0), the current through the resistor 12 is close to zero.

The voltage gain K _u for the differential output is determined by the formula

where R _H is the equivalent resistance of the load resistors 16 and 17;

S _Σ is the steepness of the conversion of voltage u _I to the collector currents of transistors 3 and 4.

Moreover, the steepness

where φ _t ≈26 mV is the temperature potential;

I ₃ - the total statistical current of the emitter circuit of the first (1) second (2) transistors (I _e1 + I _e2 = I ₃ );

_A1 = φ r _t / I _A1 - differential resistance emitter junction of transistor i-th (i = 1.2) in the statistical scheme emitter current I _ei = I _3/2.

Thus, with u _y = 0 for the circuit (figure 3).

) приращение, то это приводит к изменению тока i_R через резистор 12:If the control voltage U _y at the control input 13 receives a positive (

) increment, this leads to a change in current i _R through resistor 12:

where R ₁₂ is the resistance of the resistor 12 (R ₁₂ >> r _e31 = r _e32 ).

This current causes a decrease in the current in the common emitter circuit of transistors 1 and 2 by the value of i _R / 2, which leads to a decrease in the voltage gain from the inputs "Vh.1", "Vh.2":

With another phase of the voltage u _{y, the} coefficient K _u increases in proportion to the value of U _y .

A remarkable feature of the circuit (figure 2) is the suppression of the transmission of the control signal u _y from the input "Vh.u" to the output of the CDU. Indeed, the collector currents of transistors 3 and 4.

where i _e6 , i _e14 are the emitter currents of the composite transistors at inputs 6 and 14 (7 and 15).

Thus, the current at the output of the CDD is independent of the control signal U _y . This is a necessary condition for suppressing the signal at input 13 (u _y ) in the voltage mixers U _I and U _y .

The analytical relationships obtained above are confirmed by the results of computer modeling of the proposed KDU circuits.

The gain K _u voltage KDU (Fig.9) varies (with load resistors R ₄ = R ₅ = 1 kOhm) in the range 0 ÷ 32 (11, 12). When the resistance of the resistor R _{1 of the} circuit (FIG. 9) is increased to 500 Ω, the linearity of the control characteristic K _u = f (U _y ) and its scale along the axis U _y (FIG. 12) increase.

The characteristic (Fig. 12) shows that when U _y changes in the range of -1 V ÷ + 1 V, the common mode output voltage U _o.s. changes slightly (by 2 mV or less than 0.02%). This indicates a high suppression of the control signal U _y , which, however, has a significant effect on the gain K _{u of the} circuit.

Пример построения перемножителя, в основу которого положены две идентичные схемы (фиг.2), приведен на фиг.8.Based on the claimed KDU (FIGS. 2, 3, 6, 7), multiplying cells can be created, which, unlike the well-known Gilbert multipliers, have a wider frequency range and lower supply voltage (FIG. 7,

An example of constructing a multiplier based on two identical circuits (Fig. 2) is shown in Fig. 8.

Thus, the claimed complementary differential amplifier has electronic gain control. Moreover, the control signal u _y , as well as the input signal u _x are applied to the corresponding inputs relative to the common bus (without isolation capacitors). In addition, when using resistors as two-terminal 21, 22, 23, 24, 25 circuits (Fig.6-7) can have a supply voltage of ± 1.5 V, which allows us to recommend them for use in RF and microwave integrated circuits based on SG25H2 process technology.

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Claims (5)

1. Cascode differential amplifier with controlled amplification, containing the first (1) and second (2) input transistors whose emitters are connected to the reference current source (3), the first (4) and second (5) output composite transistors, the main emitters of which ( 6) and (7) are connected to the corresponding collectors of the first (1) and second (2) input transistors, the collectors are connected by a load circuit (8), and the bases are connected to a bias voltage source (9), characterized in that an additional transistor is introduced into the circuit (10) whose emitter is connected to an additional the source of the reference current (11) and through an additional resistor (12) is connected to the combined emitters of the first (1) and second (2) input transistors, the base is connected to the control input (13) of the cascode differential amplifier with controlled gain, and as the first ( 3) and the second (4) output composite transistors, composite transistors are used with the main (6, 7) and additional (14, 15) emitters, which are combined with each other and connected to the collector of the additional transistor (10). 2. The device according to claim 1, characterized in that each of the first (3) and second (4) output composite transistors contains a two-emitter transistor (18), and the first emitter of the two-emitter transistor is the main emitter (6, 7) of the output composite transistor, and the second emitter with an additional emitter (14, 15) of the output composite transistor. 3. The device of claim 1, wherein each of the first (3) and second (4) output composite transistors contains an auxiliary transistor (19), the emitter of which is the main emitter (6, 7) of the output composite transistor, and an additional emitter ( 14, 15) of the output composite transistor is connected to the emitter of the auxiliary transistor (19) through the auxiliary resistor (20). 4. The device according to claim 1 or 2, characterized in that the conductivity of the first (3) and second (4) output composite transistors is opposite to the conductivity of the first (1) and second (2) input transistors, the main (6, 7) and combined additional (14, 15) emitters of the output composite transistors are connected respectively with the first (21), second (22) and third (23) auxiliary sources of the reference current. 5. The device according to claim 1 or 3, characterized in that the conductivity of the first (3) and second (4) output composite transistors is opposite to the conductivity of the first (1) and second (2) input transistors, and the main (6, 7) output emitters composite transistors are connected respectively with the fourth (24) and fifth (25) auxiliary sources of the reference current.

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