RU2423779C1 - Differential amplifier with low-voltage input transistors - Google Patents

Abstract

FIELD: radio engineering. ^ SUBSTANCE: differential amplifier has an input differential stage (1) based on first (2) and second (3) output transistors, first (4) and second (5) current outputs of the input differential stage (1) connected to collectors of corresponding first (2) and second (3) input transistors, first leads of the corresponding first (6) and second (7) load resistors, as well as bases of the corresponding first (8) and second (9) output transistors, a reference current source (10), connected to combined emitters of the first (8) and second (9) output transistors, first (11) and second (12) auxiliary resistors connected between the power supply bus (13) and collectors of the corresponding first (8) and second (15) output transistors, first (14) and second (15) outputs of the device, connected to collectors of corresponding first (8) and second (9) output transistors. The second lead of the first (6) load resistor is connected to the collector of the first (8) output transistor, the second lead of the second (7) load resistor is connected to the collector of the second (9) output transistor, wherein an additional forward-biased p-n junction (17) is connected between the combined emitters of the first (6) and second (9) output transistors an the common power supply bus (16). ^ EFFECT: using new elements and connections to create conditions for operation of input transistors of a differential amplifier for which in the entire range of input signals, their collector-base voltage will vary in the range of 50-100 mV. ^ 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 for various functional purposes (for example, broadband and selective amplifiers of the high and microwave ranges).

In modern microcircuitry, differential amplifiers (DEs) containing two series-parallel parallel-balanced cascades are widely used [1-7].

The closest prototype of the claimed device is a classic two-stage remote control described in the monograph "Design and use of operational amplifiers" / translation from English. V.L. Levina and I.M. Kheyfets. / Ed. I.N. Teplyuk. - M .: Mir, 1974. - P.149, Fig.4.7

It contains an input differential stage 1 based on the first 2 and second 3 input transistors, the first 4 and second 5 current outputs of the input differential stage 1, connected to the collectors of the corresponding first 2 and second 3 input transistors, the first outputs of the corresponding first 6 and second 7 load resistors , as well as bases of the corresponding first 8 and second 9 output transistors, a reference current source 10 associated with the combined emitters of the first 8 and second 9 output transistors, the first 11 and second 12 auxiliary nye resistors connected between the power bus 13 and the collectors of the respective first 8 and second 15 output transistors, the first 14 and second 15 outputs devices connected to the collectors of the respective first 8 and second 9 output transistors.

. Это существенно снижает возможности такой архитектуры, не позволяет применять на входе ДУ так называемые «супер-β» транзисторы, для которых напряжение коллектор-база должно быть близко к нулю не только в статическом, но и в динамических режимах [8]. Кроме этого, существующие тенденции в SiGe технологиях также не допускают (в ряде случаев) использовать режимы работы входных СВЧ-транзисторов 2 и 3 при граничной частоте f_т=200÷300 ГГц с изменяющимся на 1÷2 В под действием входного сигнала напряжением коллектор-база.A significant disadvantage of the known device of figure 1 is that its input transistors 2 and 3 must be sufficiently high voltage, i.e. have a breakdown voltage of the pn junction collector-base exceeding the voltage of the collector power source

. This significantly reduces the capabilities of such an architecture and does not allow the use of so-called “super-β” transistors at the remote control input, for which the collector-base voltage should be close to zero not only in static but also in dynamic modes [8]. In addition, existing trends in SiGe technologies also do not allow (in some cases) the use of the operating modes of input microwave transistors 2 and 3 at a cutoff frequency f _t = 200–300 GHz with a collector voltage of 1–2 V, which is changed by the input signal base.

The main objective of the invention is to create, due to new elements and the connections between them, such operating conditions for the input transistors of the remote control, under which their collector-base voltage will vary in the range of 50-100 mV over the entire range of input signals. This will make it possible to use bipolar structures with a low collector-base voltage as the active element data and thus obtain new device qualities — an ultra-low input current due to the high β values of the applied low-voltage transistors [8], low noise, and a higher frequency range due to use of SiGe technologies, etc.

The problem is solved in that in the differential amplifier of figure 1, containing the input differential stage 1 based on the first 2 and second 3 input transistors, the first 4 and second 5 current outputs of the input differential stage 1, associated with the collectors of the corresponding first 2 and second 3 input transistors, the first conclusions of the corresponding first 6 and second 7 load resistors, as well as the bases of the corresponding first 8 and second 9 output transistors, a reference current source 10 connected to the combined emitters first 8 and second 9 output transistors, the first 11 and second 12 auxiliary resistors connected between the power bus 13 and the collectors of the corresponding first 8 and second 15 output transistors, the first 14 and second 15 device outputs associated with the collectors of the corresponding first 8 and second 9 output transistors, new elements and connections are provided - the second terminal of the first 6 load resistor is connected to the collector of the first 8 output transistor, the second terminal of the second 7 load resistor is connected to the collector of the second 9 output t a transistor, and between the combined emitters of the first 6 and second 9 output transistors and a common bus of power supplies 16, an additional forward biased pn junction 17 is included.

Figure 1, 2 shows a diagram of the remote control prototype (figure 1) and the claimed remote control (figure 2).

Figure 3 shows a diagram of the claimed remote control in a Cadence environment on models of SiGe transistors (SGB25VD).

The graphs of figure 4 characterize the dependence of the voltages on the collectors of the input transistors from the input signal in the circuit of figure 3.

The graphs of figure 5 show the dependence of the voltages at the outputs of the device of figure 3 from the input signal, and the graph of figure 6 is the amplitude-frequency characteristic of the remote control of figure 3.

A differential amplifier with low-voltage input transistors contains an input differential stage 1 based on the first 2 and second 3 input transistors, the first 4 and second 5 current outputs of the input differential stage 1, connected to the collectors of the corresponding first 2 and second 3 input transistors, the first conclusions corresponding to the first 6 and the second 7 load resistors, as well as the bases of the corresponding first 8 and second 9 output transistors, a reference current source 10 associated with the combined emitters of the first 8 and the second 9 output transistors, the first 11 and second 12 auxiliary resistors connected between the power bus 13 and the collectors of the corresponding first 8 and second 15 output transistors, the first 14 and second 15 device outputs associated with the collectors of the corresponding first 8 and second 9 output transistors . The second terminal of the first 6 load resistor is connected to the collector of the first 8 output transistor, the second terminal of the second 7 load resistor is connected to the collector of the second 9 output transistor, and an additional forward biased pn- is connected between the combined emitters of the first 6 and second 9 output transistors and the common bus of power supplies 16 transition 17.

Consider the work of the known (figure 1) and the claimed (figure 2) remote control. In the remote control prototype of FIG. 1, the voltage across the collectors of the input transistors 2 and 3 in static mode is determined by the formulas:

where I _k2 , I _k3 are the collector currents of the input transistors 2 and 3, which can vary under the influence of a signal in the range 0 ÷ 2I ₀ (I ₁ = 2I ₀ - static current of the common emitter circuit of the input differential stage 1).

, и, следовательно, входные транзисторы ДУ фиг.1 должны иметь напряжение пробоя, превышающее

.The extreme values {0, 2I ₀ } of the collector currents I _k2 and I _k3 are taken with input signals u _in > ± 50 mV. Therefore, the voltage at the collectors of the input 2 and 3 transistors of the remote control of FIG. 1 in operating modes can reach values (1) and (2) close to the collector supply voltage

, and therefore, the input transistors of the remote control of figure 1 must have a breakdown voltage exceeding

.

In the inventive device of figure 2, the voltage across the collectors of the input transistors 2 and 3 practically does not change, since it does not depend on the numerical values of the collector currents I _k2 and I _k3 :

It should be noted that the voltage at the emitter pn junctions of the transistors has a logarithmic dependence on the emitter currents:

where φ _t ≈25 mV is the temperature potential;

U _xx.i is the voltage at the emitter junction at an emitter junction current I _ei = I _xx (for example, for many silicon transistors U _xx = 0.51 V at I _xx = 1 μA).

Thus, it follows from (3) - (5) that

/R₁₁. При I_к2.max=2I₀ выполняется условие:The range of variation of the emitter current of the transistor 8 depends on the range of variation of the collector current of the first 2 input transistor. If I _k2.min ≈0, then I _e8.max ≈

/ R ₁₁ . When I _k2.max = 2I ₀ the condition is satisfied:

That is, the minimum eitter current of transistor 8:

Considering that the current through the pn junction 17 does not practically change, one can find the extreme values of the voltage at the collector of the first 2 input transistor:

Given the latest relations, we find that the voltage variation range on the collector of transistor 2

, то «теоретический» перепад напряжения ΔU_к2 не будет превышать ΔU_к2=8÷15 мВ.If, for example, choose 2I ₀ (R ₆ + R ₁₁ ) = 0.5

, then the “theoretical” voltage drop ΔU _k2 will not exceed ΔU _k2 = 8 ÷ 15 mV.

Thus, in the claimed circuit, the input transistors 2 and 3 operate with small changes in the voltage on the collector and can be low voltage.

The voltage at the output of Output 1 of the remote control of FIG. 2 can take two extreme values under the action of a signal

Thus, the dynamic range of the output differential voltage of the remote control of figure 2

Presented in Fig.6, the results of computer simulations confirm these theoretical conclusions - the voltage at the collectors of the input transistors 2 and 3 change by no more than 70 mV. The range of the restriction of the output signals (5) ΔU _O ≈0,9 B, a frequency control range - 9.1 GHz.

Information sources

1. US patent application No. 2010/0102884 fig.2.

2. US Patent No. 3,970.947.

3. US patent No. 4.97439.696.

4. US patent No. 5.550.512 fig.2.

5. Operational amplifiers with a direct connection of cascades [Text] / V.I. Anisimov, M. V. Kapitonov, N. N. Prokopenko, Yu. M. Sokolov - L., 1979. - P.145, Fig. 145.

6. Rutkowski, J. Integrated Operational Amplifiers. Reference Guide [Text] / J. Rutkowski; translation from English B.N. Bronin; under the editorship of M.V. Galperina. - M .: Mir, 1978. - Fig. 1.9 (Fig. 1.20).

7. Design and use of operational amplifiers [Text] / translation from English. V.L. Levina and I.M. Kheyfets; under the editorship of I.N. Teplyuk. - M .: Mir, 1974. - P.158 (Fig.4.10), P.145 (Fig.4.4).

8. Halperin M.V. DC Amplifiers [Text] / M.V. Halperin, Yu.P. Zlobin, V.A. Pavlenko. - Ed. 2nd, rev. and add. - M .: Energy, 1978.- 248 p., Ill. - S. 82-83.

Claims (1)

A differential amplifier with low-voltage input transistors containing an input differential stage (1) based on the first (2) and second (3) input transistors, the first (4) and second (5) current outputs of the input differential stage (1) connected to the collectors of the corresponding the first (2) and second (3) input transistors, the first terminals of the corresponding first (6) and second (7) load resistors, as well as the bases of the corresponding first (8) and second (9) output transistors, a reference current source (10), associated with united em tters of the first (8) and second (9) output transistors, the first (11) and second (12) auxiliary resistors connected between the power bus (13) and the collectors of the corresponding first (8) and second (15) output transistors, the first (14 ) and the second (15) outputs of the device associated with the collectors of the corresponding first (8) and second (9) output transistors, characterized in that the second terminal of the first (6) load resistor is connected to the collector of the first (8) output transistor, the second terminal of the second (7) the load resistor is connected to the collector of the second (9) in an output transistor, and between the combined emitters of the first (6) and second (9) output transistors and a common bus of power supplies (16) an additional forward biased pn junction is included (17).

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