RU2421882C1 - Two-cascade hf-amplifier - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: two-cascade HF-amplifier includes input transistor (1) as per the diagram with common emitter the base of which is connected as to alternating current to signal source (2) and the first output of setup circuit of static mode of the first cascade (3), the output transistor (4) the emitter of which is connected to collector of input transistor (1); base is connected to the second output of setup circuit of static mode of the first cascade (3), and collector is connected through correction inductance (5) to bus (6) of power source, the second amplification cascade (7) the input of which is connected through separating capacitor (8) to collector of output transistor (4) and to the first output of resistor of setup circuit of static mode of the second cascade (9). The second output of resistor of setup circuit of static mode of the second cascade (9) is connected to emitter of output transistor (4). ^ EFFECT: reducing the influence of setup circuit of static mode of the second amplification cascade on the main parameters of the device. ^ 4 cl, 13 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, broadband, RF and microwave amplifiers, filters).

In modern devices of radio communications and telecommunications, amplification cascades on transistors are widely used, connected according to the “common emitter” circuit (common source) or to the cascode “common emitter - common base” circuit, in which the correcting inductance (sometimes the oscillatory circuit) plays the role of the collector load. This is the basic architecture of various radio receivers and radio transmitting devices, which has become the basis of many electronic products [1-7].

In the practical use of such RF and microwave amplifiers as two-stage devices with corrective inductance in the first stage, the problem arises of minimizing the influence of the input resistance (R _in ) of the second amplification stage on the quality factor Q of the oscillating circuit of the input stage and the overall gain of the two-stage structure (K _y ) [ fourteen]. To obtain Q = Q _max and K _y = K _{y max,} it is necessary to have R _in → ∞. However, in practical circuits, R _I is determined by the resistors of the static mode of the second amplification stage, which have to be selected with high resistance. Such a solution should not be considered optimal, because an increase in the resistances of the resistors in the base circuit of the input transistor of the second amplification stage leads to a deterioration of a number of its parameters (stability of the static mode, noise, total area occupied by resistors on the substrate, etc.).

The second direction of solving this problem is the use of transformer coupling with a second cascade of amplification [3, 6] or the so-called incomplete inclusion of an oscillatory circuit [1] (or corrective inductance with a tap). However, this complicates the manufacturing technology of the inductance and the device as a whole.

The closest in technical essence to the claimed device includes a multi-stage cascade RF amplifier, proposed in the patent of Germany No. 1.512.725 fig.3. It contains the input transistor 1 according to the scheme with a common emitter, the base of which is connected via alternating current to the signal source 2 and the first output of the static mode establishment circuit of the first stage 3, the output transistor 4, the emitter of which is connected to the collector of the input transistor 1, the base is connected to the second output the circuit for establishing the static mode of the first stage 3, and the collector is connected to the bus of the power supply 6 through the corrective inductance 5, the second amplification stage 7, the input of which is connected through the isolation capacitor 8 is connected to the collector of the output transistor 4 and is connected with the first output of the resistor of the static circuit of the second stage 9.

A significant drawback of the well-known two-stage RF amplifier (RF) is that in it the circuit for establishing the static mode of the second amplification stage has a negative shunt effect on the first (input) stage. As a result, in the two-stage amplifier of FIG. 1, the main parameters deteriorate - the Q factor (when constructing a selective amplifier), the maximum voltage gain, noise, etc.

The main objective of the invention is to reduce the influence of the circuit establishing the static mode of the second amplification stage of the RFI on the main parameters of the device.

An additional goal is to simplify the circuit for establishing the static mode of the second RF amplification stage.

The problem is solved in that in a two-stage RF amplifier containing an input transistor 1 according to a circuit with a common emitter, the base of which is connected by an alternating current to a signal source 2 and the first output of the static circuit establishing the first stage 3, the output transistor 4, the emitter of which is connected with the collector of the input transistor 1, the base is connected to the second output of the circuit establishing the static mode of the first stage 3, and the collector through the corrective inductance 5 is connected to the bus of the power source 6, the second stage gain 7, the input of which is connected through the isolation capacitor 8 to the collector of the output transistor 4 and is connected to the first output of the resistor of the static circuit of the second stage 9, new elements and connections are provided - the second output of the resistor of the static circuit of the second stage 9 is connected to the emitter of the output transistor four.

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

Figure 3 shows a diagram of the inventive RFI in accordance with paragraph 3, and figure 4 - paragraph 4 of the claims.

In Fig.5 shows a diagram of the inventive RFI of Fig.2 in the computer simulation environment of Cadence on models of HJW integrated transistors, and Fig.6 is a graph of the frequency dependence of its voltage gain.

The diagram of the RFI prototype of FIG. 1 in the Cadence environment is shown in FIG. 7.

On Fig shows the amplitude-frequency characteristics of the compared circuits of Fig.5 and Fig. 7.

Figure 9 shows a modified circuit of the inventive device of figure 2 in a computer simulation environment Cadence on models of integrated transistors HJW.

Figure 10 shows the amplitude-frequency characteristics of the compared RFs of Fig.7 and Fig.9.

In Fig.11 shows a diagram of the proposed RFI of Fig.4 in the computer simulation environment Cadence on models of integrated transistors HJW.

In Fig.12 shows the amplitude-frequency characteristic of the RFI of Fig.11, and Fig.13 is a graph of the frequency dependence of K _{for the} circuit of Fig.11 for different values of the resistance of the resistor R ₁₄ = R ₈ = R.

The two-stage RF amplifier of FIG. 2 contains an input transistor 1 according to a circuit with a common emitter, the base of which is connected via alternating current to a signal source 2 and the first output of the static mode establishment circuit of the first stage 3, the output transistor 4, the emitter of which is connected to the collector of the input transistor 1 , the base is connected to the second output of the static mode establishment circuit of the first stage 3, and the collector is connected to the power supply bus 6 through the corrective inductance 5, the second amplification stage 7, the input of which is through the capacitor 8 is connected to the collector of the output transistor 4 and is connected to the first output of the static circuit resistor of the second stage 9. The second output of the static circuit resistor of the second stage 9 is connected to the emitter of the output transistor 4. Here, the static circuit of the first stage 3 contains in a particular case, the current source 11, pn junctions 12 and 13, the capacitor 14 and the resistor 15.

In addition, in Fig. 2, in accordance with claim 2, the second amplification stage 7 is made on the first additional transistor 16 according to the scheme with a common emitter, the base of which is the input of the second amplification stage 7, and the collector is connected through the first 17 additional load two-pole with the power supply bus 6 and connected to the output of the device.

In figure 3, in accordance with claim 3 of the claims, the second amplification stage 7 is made according to the cascode “common emitter - common base” circuit on the second 18 and third 19 additional transistors, and the collector of the third 19 additional transistor is connected to the power supply bus 6 through the second 20 additional bipolar load, and the base of the third 19 additional transistor is connected to the base of the output transistor 4.

In Fig. 4, in accordance with claim 4 of the claims, the second amplification stage 7 is made on the field effect transistor 25 according to a circuit with a common source, the gate of which is the input of the second amplification stage 7, and the circuit for establishing the static mode of the first stage contains elements 21, 22, 23 and 24.

Consider first the operation of the RF amplifier of FIG. 2 with direct current.

The static collector current of the input transistor 1 is determined by the circuit establishing its static mode 3:

where I _k1 = I _k4 - collector currents of transistors 1 and 4;

I ₁₁ - bipolar current 11.

The static mode of the input transistor 16 of the second amplification stage 7 is determined by the voltage U ₂ at the second output of the static mode 3 establishment circuit and, for small resistances of the resistor 9, is found by the formula

where I _k16 - collector current of the transistor 16.

Thus, in the proposed circuit of figure 2, the static currents of the transistors 1, 4, 16 are determined by the bipolar circuit 11 of the establishment of the static mode of the first stage 3. Moreover, the temperature stability of these currents is quite high due to the same temperature drift of the voltage across the diodes 12, 13, on the one hand , and the emitter-base voltages of transistors 4 and 16, on the other.

Let us further consider the operation of the circuit on alternating current. Let the output voltage of the first stage and, therefore, the input u _{b.16 of the} second amplification stage have a positive increment. This leads to an increase in the value of i _{9 of the} current through the resistor 9, which is transmitted to the emitter, then to the collector of the transistor 4 and, further, through the isolation capacitor 8 to the input of the second stage 7:

where α ₄ = 0.98-0.99 is the current gain of the emitter of transistor 4;

R ₉ is the resistance of the resistor 9.

Therefore, the effective value of the resistance of the resistor 9 of the circuit establishing the static mode of the second stage increases

For example, if R ₉ = 1 kOhm, then R _9.eff = 50 ÷ 100 kOhm.

Thus, despite the small values of the resistance of the resistor of the establishment of the static mode of the second stage (R9), which determines the static mode of the second stage of amplification 7, its effect on the gain and other parameters of the two-stage device of FIG. 2 is attenuated by one or two orders of magnitude.

These findings are confirmed by computer simulation of the circuits of figure 5, 7, 9, 11, presented in figure 10, 12, 13.

Thus, the proposed two-stage RF amplifier has significant advantages in comparison with the prototype.

Information sources

1. Agahanyan T.M. Designing Electronic Devices with Integrated Operational Amplifiers: A Training Manual. - M .: MEPhI, 2008 .-- S.742-746.

2. Falkovich S.E., Music of Z.N. Sensitivity of transceiver amplifiers. - M .: Energy, 1970. - S.115-116, Fig. 41, 42.

3. Krylov G.M., Vishnevskaya A.V. Design of logarithmic amplifiers with continuous signal detection. - M.: Energy, 1970.- 144 p., Fig. 42, p. 98.

4. Gorban B.G. Broadband transistor amplifiers. - M .: Energy, 1975.- C.139, Fig. 5-5.

5. Germany patent No. 1512725, fig.3.

6. Korolev V.I., Kuchumov A.I. Teacher Limiters. - M.: Energy, 1976. - P.102, Fig. 51, p. 100, Fig. 47.

7. US Patent No. 6127984, fig. 3.

Claims (4)

1. A two-stage RF amplifier containing an input transistor (1) according to the scheme with a common emitter, the base of which is connected by an alternating current to a signal source (2) and the first output of the circuit for establishing the static mode of the first stage (3), the output transistor (4), the emitter of which is connected to the collector of the input transistor (1), the base is connected to the second output of the static mode circuit of the first stage (3), and the collector is connected to the power supply bus (6) through the corrective inductance (5), the second amplification stage (7), whose input is Without a separation capacitor (8) connected to the collector of the output transistor (4) and connected to the first output of the resistor of the static circuit of the second stage (9), characterized in that the second output of the resistor of the static circuit of the second stage (9) is connected to the output emitter transistor (4). 2. A two-stage RF amplifier according to claim 1, characterized in that the second amplification stage (7) is made on the first additional transistor (16) according to a circuit with a common emitter, the base of which is the input of the second amplification stage (7), and the collector through the first (17) an additional bipolar load is connected to the bus of the power source (6) and connected to the output of the device. 3. The two-stage RF amplifier according to claim 1, characterized in that the second amplification stage (7) is made according to the cascode scheme “common emitter - common base” on the second (18) and third (19) additional transistors, and the collector of the third (19 ) the additional transistor is connected to the bus of the power source (6) through the second (20) additional two-pole load, and the base of the third (19) additional transistor is connected to the base of the output transistor (4). 4. Two-stage RF amplifier according to claim 1, characterized in that the second amplification stage (7) is made on a field-effect transistor (25) according to a circuit with a common source, the gate of which is the input of the second amplification stage (7).

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