RU2571369C1 - Cascode amplifier with extended frequency band - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: device includes an input voltage-to-current converter, the current output of which is connected to the emitter of an output transistor, a bias voltage source connected to the base of the output transistor, a two-terminal element of a collector load connected between the power supply bus and the output of the device, which is connected to the collector of the output transistor. The output of the device is connected to the input of an additional current amplifier through an additional balancing capacitor, wherein the output of the additional current amplifier is connected to the emitter of the output transistor.

EFFECT: extending the operating frequency range of the cascode amplifier without deterioration of voltage gain.

5 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 and selective amplifiers of the high and microwave ranges).

In modern microelectronics, classical cascode amplifiers (KUs) with a resistive (or inductive) load included in the collector circuit of an output transistor – cascade with a common base are widely used [1-21].

Closest to the technical nature of the claimed device is KU fig. 1 according to Spanish patent ES 2.079.397, fig. 9.

A significant drawback of the well-known KU, the architecture of which is also present in many other patents [1-21], is that it does not have high enough upper cutoff frequency (f _in -3 dB level). This is due to the negative influence of stray capacitance on the substrate (C _p ) of the output transistor and its collector-base capacitance (C _kb ). The numerical values of C _p and C _kb for technological processes having, for example, increased radiation resistance, are one of the main factors that determine the frequency range of broadband amplifiers based on KU of FIG. one.

The main objective of the invention is to expand the range of operating frequencies of the KU without deterioration of the voltage gain.

The problem is solved in that in the cascode amplifier of FIG. 1, containing an input voltage-current converter 1, the current output of which is connected to the emitter of the output transistor 2, a bias voltage source 3 connected to the base of the output transistor 2, a collector load 2-pole 4 connected between the power supply bus 5 and the output of the device 6, which is connected to the collector of the output transistor 2, new elements and connections are provided - the output of the device 6 is connected to the input of an additional current amplifier 7 through an additional correction capacitor 8, and the output is supplemented The current amplifier 7 is connected to the emitter of the output transistor 2.

A prototype amplifier circuit is shown in FIG. 1. The circuit of FIG. 1b has a typical construction of a voltage-current converter 1. In the drawing of FIG. 2 presents a diagram of the inventive device in accordance with paragraphs. 1 and 2 of the claims.

In the drawing of FIG. 3 is a diagram of the inventive device of FIG. 2 in the environment of PSpice on models of integrated transistors of OJSC “Research Institute of Pulsar” with specific implementation of the main functional units.

In the drawing of FIG. 4 shows the amplitude-frequency characteristic of the voltage gain of the gain factor of FIG. 3 at different values of the capacitance of the correction capacitor C _k (capacitor 8 in the notation of Fig. 2). From these graphs it follows that the operating frequency range of the claimed cascode amplifier extends more than 5 times.

The extended-range cascode amplifier of FIG. 2 contains an input voltage-current converter 1, the current output of which is connected to the emitter of the output transistor 2, a bias voltage source 3 connected to the base of the output transistor 2, a collector load 4-terminal, connected between the power supply bus 5 and the output of the device 6, which connected to the collector of the output transistor 2. The output of the device 6 is connected to the input of the additional current amplifier 7 through an additional correction capacitor 8, and the output of the additional current amplifier 7 is connected to the emitt py output transistor 2. Deflection capacitor 9 simulates the effect on f _{in the} parasitic capacitance of the transistor on the substrate 2 and the load capacitance, and a parasitic capacitor 10 - capacitance of the transistor collector-base 2.

In the drawing of figure 2, in accordance with paragraph 2 of the claims, the additional current amplifier 7 has a low input and high output impedance, and its current transfer coefficient is greater than unity.

Consider the operation of the control unit of FIG. 2.

In the high-frequency region, the amplitude-frequency characteristic of the CS of FIG. 2, the stray capacitance begins to affect the substrate 9 in the collector circuit of transistor 2 and the collector-base capacitance 10 of transistor 2, through which stray current components flow:

, $${\dot{I}}_{10}$$

- комплексы токов через паразитные конденсаторы 9 и 10;Where $${\dot{I}}_9$$

, $${\dot{I}}_{10}$$

- complexes of currents through stray capacitors 9 and 10;

- комплекс напряжения на выходе устройства 6;

- voltage complex at the output of device 6;

- комплексное сопротивление паразитного конденсатора 9 на частоте сигнала ω; $${\dot{Z}}_9=\frac{\mathrm{one}}{j\omega C_9}$$

- the complex resistance of the parasitic capacitor 9 at a signal frequency ω;

- комплексное сопротивление паразитного конденсатора 10 на частоте сигнала ω. $${\dot{Z}}_{10}=\frac{\mathrm{one}}{j\omega C_{10}}$$

- the complex resistance of the parasitic capacitor 10 at the frequency of the signal ω.

создает в дополнительном корректирующем конденсаторе 8 комплекс токаVoltage $${\dot{U}}_{\mathrm{at}sx}$$

creates a current complex in an additional correction capacitor 8

- комплекс сопротивления дополнительного корректирующего конденсатора 8.Where $${\dot{Z}}_8=\frac{\mathrm{one}}{j\omega C_8}$$

- resistance complex additional correction capacitor 8.

и тока коллектора транзистора 2: $${\dot{I}}_{к2}=K_i{\alpha }_2{\dot{I}}_{ск}$$

, где α₂ - коэффициент усиления по току эмиттера выходного транзистора 2, Ki - коэффициент усиления по току дополнительного усилителя тока 7 (K_i≥1). Действительно, в достаточно широком диапазоне частот в схеме фиг. 2 можно обеспечить равенствоThe current increment through the capacitor 8 is transmitted to the emitter, and then to the collector of transistor 2. Therefore, in the collector circuit of transistor 2, mutual compensation of the sum of currents is provided $${\dot{I}}_9+{\dot{I}}_{10}$$

and collector current of transistor 2: $${\dot{I}}_{\mathrm{to}2}=K_i{\alpha }_2{\dot{I}}_{\mathrm{from}\mathrm{to}}$$

where α ₂ is the current gain of the emitter of the output transistor 2, Ki is the current gain of the additional current amplifier 7 (K _i ≥1). Indeed, over a wide enough frequency range in the circuit of FIG. 2 equality can be ensured

Therefore, necessary to increase f _{in the} capacity of the additional correction capacitor 8 is calculated by the formula

where K _i α ₂ > 1.

Ultimately, when condition (4) is satisfied, the operating frequency range of the control unit of FIG. 2 is expanding. This conclusion is confirmed by the results of computer simulation of FIG. four.

Thus, the claimed circuit design of the cascode amplifier is characterized by a higher range of operating frequencies.

BIBLIOGRAPHIC LIST

1. US Patent No. 6,825,723 fig. 3

2. US Patent No. 4,151.483 fig. 2

3. US Patent No. 4,151.484

4. US Patent No. 3,882,410 fig. 3

5. Patent application WO 2004/030207

6. US patent No. 4.021.749 fig. 2

7. US Patent No. 3,693.108 fig. 9

8. US Patent No. 7.113.043 fig. 2

9. US Patent Application 2006/0033562

10. US Patent Application 2006/0132242

11. US Patent Application 2006/0119435

12. US Patent Application 2005/0248408

13. US patent No. 6.204.728

14. US Patent No. 6,278.329

15. US patent application 2005/0225397

16. US Patent No. 5,451.906

17. US Patent No. 7,098.743 fig. one

18. British Patent GB No. 1431481 fig. 2

19. US Patent No. 6,515,547 fig. 2

20. Patent application US 2010/0283543 fig. one

21. Patent ES 2.079.397, fig. 9.

Claims (2)

1. A cascode amplifier with an extended frequency range, containing an input voltage-current converter (1), the current output of which is connected to the emitter of the output transistor (2), a bias voltage source (3) connected to the base of the output transistor (2), two-terminal a collector load (4) connected between the bus of the power source (5) and the output of the device (6), which is connected to the collector of the output transistor (2), characterized in that the output of the device (6) is connected to the input of an additional current amplifier (7) through additional to rrektiruyuschy capacitor (8), wherein the additional current of the amplifier output (7) is connected to the emitter of the output transistor (2). 2. A cascode amplifier with an extended frequency range according to claim 1, characterized in that the additional current amplifier (7) has a low input and high output impedance, and its current transfer coefficient is greater than unity.

Images