RU2523953C1 - Instrumentation amplifier with resonance amplitude-frequency characteristic - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: proposed amplifier incorporates the components that follow: input signal source (1), base of first input transistor (2), second input transistor (3), device output (4), first current-stabilising dipole (5), first power supply bus (6), current mirror (7), second power supply bus (8), output (9), second current-stabilising dipole (10), first correcting capacitor (11), common bus of power supplies (12), second correcting capacitor (13), input (14) and extra resistor (15).

EFFECT: lower output signal attenuation at higher and stable Q factor of AF characteristic, higher voltage gain in quasiresonance frequency f₀.

6 dwg

Description

The present invention relates to the field of measuring equipment, radio engineering and communications and can be used in devices for filtering radio signals, television, radar, including for the purpose of measuring the parameters of high-frequency signals, etc.

Integrated operational amplifiers with special RC-correction elements that form the amplitude-frequency characteristic of the resonance type are widely used today in the problems of measuring and isolating high-frequency signals [1, 2]. However, the classical construction of such measuring amplifiers (DUTs) is accompanied by significant energy losses, which are mainly used to ensure the static mode of a sufficiently large number of secondary transistors forming an operational amplifier [1, 2]. In this regard, it is very urgent to build a DUT on the smallest possible number of transistors, providing a narrow spectrum of signals with a sufficiently high quality factor (Q) of the resonant characteristic (Q = 2 ÷ 10) at low power consumption.

Known schemes are DUTs integrated into the architecture of RC filters based on bipolar transistors, which provide the formation of the amplitude-frequency characteristics of the voltage gain in a given frequency range Δf = f _in -f _n [3-10]. Moreover, their upper cutoff frequency f _{in is} sometimes formed by the inertia of the transistors of the circuit (capacitance per substrate), and the lower f _n is determined by a special correcting capacitor.

The closest prototype of the claimed device is the DUT presented in patent US 4.843.343 fig.1. It contains an input signal source 1 connected to the base of the first 2 input transistor, the second 3 input transistor, the base of which is connected to the output 4 of the device, and the emitter is connected to the emitter of the first 2 input transistor and through the first 5 current-stabilizing two-terminal device is connected to the first 6 bus of the power source , current mirror 7, coordinated with the second 8 bus power supply, the output of which 9 through the second 10 current-stabilizing two-terminal connected to the first 6 bus power source, the first 11 correction capacitor is included between the output of the first unit 4 and the power supply common bus 12, a second adjustment capacitor 13.

To ensure a large (K _y = 10 ^-2 ÷ 10 ^-4 ) attenuation of the output signal in the low frequency range (f << f ₀ ) in the structure of the DUT of Fig. 1, it is necessary to use the connection of signal source 1 to the base of the first 2 input transistor through a special input isolation capacitor, the capacity of which should be significantly larger than the capacitances of the frequency-setting circuit (first 11 and second 13 correcting capacitors). In addition, in this case, an additional mode-setting resistor is required in the base circuit of the input transistor 2.

Significant disadvantages of the Yiwu prototype of figure 1 are as follows:

- for cascading (serial connection) of such DUT schemes into bandpass filters, it is necessary to use additional buffer amplifiers;

- in the structure of figure 1 it is problematic to obtain high quality factors. When implementing high Q factors (Q = 3 ... 10), it is necessary to use a large value of the resistance of the second current-stabilizing two-terminal 10, which increases the proportion to the parasitic capacitance of the collector junction of the transistor 3 and the output capacitance of the current mirror. Ultimately, this limits the operating frequency range of the DUT prototype.

The main objective of the invention is to increase the attenuation of the output signal in the low frequency range with an increased and sufficiently stable quality factor Q of the amplitude-frequency characteristic (AFC) of the DUT and a large voltage gain (K ₀ ) at the quasi-resonance frequency f ₀ .

The problem is solved in that in the DUT of FIG. 1, containing an input signal source 1 connected to the base of the first 2 input transistor, a second 3 input transistor, the base of which is connected to the output 4 of the device, and the emitter is connected to the emitter of the first 2 input transistor and through the first 5 current-stabilizing bipolar is connected to the first 6 bus of the power supply, a current mirror 7, coordinated with the second 8 bus of the power supply, the output of which 9 through the second 10 current-stabilizing bipolar is connected to the first 6 bus of the power source , the first 11 correction capacitor connected between the output 4 of the device and the common bus of the power sources 12, the second 13 correction capacitor, new elements and connections are provided - field-effect transistors are used as the first 2 and second 3 input transistors, the drain of which corresponds to the collector, and the source to the emitter and the gate to the base of the bipolar transistor, the drain of the second 3 input transistor is connected to the input 14 of the current mirror 7, the output 9 of the current mirror 7 is connected to the output of the device 4 through the second 13 correction condensate Oh, and the drain of the first 2 input transistor is connected to the second 8 bus of the power source, and the output of the device 4 is shunted by alternating current with an additional resistor 15.

The amplifier circuit of the prototype is shown in the drawing of figure 1. In the drawing of figure 2 presents a diagram of the claimed IU in accordance with the claims.

In the drawing of figure 3 presents a diagram of the IUT of figure 2 with a specific implementation of the current mirror 7.

The drawing of FIG. 4 shows a diagram of the DUT of FIG. 3 in a Cadence computer simulation environment on SiGe integrated transistor models.

The drawing of figure 5 shows the logarithmic amplitude-frequency characteristic of the DUT of figure 4 in the frequency range of 0.1-10 GHz at different values of the current I ₀ current-stabilizing two-terminal 5.

The drawing of Fig.6 shows the logarithmic phase-frequency characteristic of the DUT of Fig.4 in the frequency range of 0.1-5 GHz at different current values I _{0 of the} current-stabilizing two-terminal 5.

The measuring amplifier with a resonant amplitude-frequency characteristic of FIG. 2 contains an input signal source 1 connected to the base of the first 2 input transistor, a second 3 input transistor, the base of which is connected to the output 4 of the device, and the emitter is connected to the emitter of the first 2 input transistor and through the first 5, the current-stabilizing two-terminal device is connected to the first 6 bus of the power source, the current mirror 7, coordinated with the second 8 bus of the power source, the output of which 9 is connected through the second 10 current-stabilizing two-terminal device 6, the first power source bus, the first adjustment capacitor 11 connected between the output device 4 and the power supply common bus 12, a second adjustment capacitor 13. Field-effect transistors are used as the first 2 and second 3 input transistors, the drain of which corresponds to the collector, the source to the emitter, and the gate to the base of the bipolar transistor. The drain of the second 3 input transistor is connected to the input 14 of the current mirror 7, the output 9 of the current mirror 7 is connected to the output of the device 4 through the second 13 correction capacitor, and the drain of the first 2 input transistor is connected to the second 8 bus of the power supply, and the output of the device 4 is shunted by a variable current additional resistor 15.

Consider the work of the proposed scheme of figure 3.

The input source u _BX (1) changes the currents of the differential pair implemented on transistors 2 and 3. Changing the drain current of transistor 3 causes a change in the currents of bipolar transistor 17. The collector load of this transistor, formed by resistors 10, 15 and capacitors 11, 13, leads to the frequency dependence of the voltage across the resistor 15, the corresponding frequency response and phase response of the selective amplifier. Indeed, the effect of the capacitive divider on the capacitors 13 and 11 weakens the currents of the resistor 15 in the low and high frequency ranges in the vicinity of the quasi-resonance frequency f ₀ . The output voltage of the DUT (node 4) differentially interacts with the input voltage 1 and changes the drain current of the transistor 3 and, therefore, the base current of the transistor 17. Thus, the connection of the output circuit 4 of the DUT to the gate of the transistor 3 implements a feedback loop in the circuit, the frequency dependence of which corresponds to the characteristics of the RTU. The depth of this feedback (OS) is maximum at only one frequency, which corresponds to the frequency of the quasi-resonance (f ₀ ) of the DUT. Due to the regenerative properties of this OS, the Q factor (Q) and the gain of the DUT (K ₀ ) increase without changing the frequency of quasi-resonance f ₀ .

Integrated transmission ratio DUT 2 as the ratio of the output voltage u _vyh.4 (output device - node 4) to the input voltage u _Rin of the amplifier is determined by a formula which can be obtained by electronic circuits assays

where f is the frequency of the input signal;

f ₀ is the frequency of the quasi-resonance of the DUT;

Q - quality factor of the frequency response of the emitter;

K ₀ is the gain of the DUT in terms of voltage at the frequency of quasi-resonance f ₀ . Moreover

;Where

;

S ₂ ≈ S ₃ ≈S ₁₆ - the steepness of field-effect transistors 2, 3, 16;

h11.17≈φ _t / I ₀ is the input resistance of the transistor 17 in a circuit with a common base at a static emitter current I _e = I ₀ ;

φ _t ≈26 mV - temperature potential.

From formula (4) it follows that by changing the equivalent slope S, it is possible, independently of the realized value f ₀ (2), to configure Q of the DUT circuit for a given value. For example, in the circuit of FIG. 3, this is easily realized by changing the current I ₅ = 2I _{0 of the} two-terminal network 5. Indeed, with a relatively high identity of field-effect transistors of the circuit S = 1 / h _11.17 ≈I ₀ / φ _t . Therefore, the deep attenuation of the input signal in the low frequency range (f << f ₀ ) provided by the claimed circuit does not contradict the property of controllability by the Q factor Q.

In addition, an important additional property of the circuits of Fig.2-Fig.3 is the relatively small effect of parasitic capacitances of transistors on the main parameters (f ₀ , Q). Indeed, for the circuit of FIG. 3, it can be shown that the relative changes in the main parameters of the DUT

where C _I - the input capacitance of the transistor 3;

C _p - the capacitance on the substrate of the output circuit of the current mirror 7 (collector circuit of the transistor 17, figure 3).

The structural properties of the circuit of figure 3 (figure 2) allow you to optimize the parameters of the DUT of figure 3 (figure 2). If we choose C ₁₁ = C ₁₃ = C, then the optimal ratio (R ₁₅ / R ₁₀ ) _opt = 1/2, and then with the minimum value of the equivalent slope S, the condition

In this case, the sensitivity of the main parameters of the DUT to the instability of passive circuit elements are optimized:

In the bipolar basis of the elements in the DUT circuit of FIG. 2, FIG. 3, to reduce the direct transmission of the input signal at low frequencies of the circuit “base of transistor 2 - emitter of transistor 2 - emitter of transistor 3 - base of transistor 3”, depending on their current gain base (β = 50 ÷ 200) need an additional separation capacity in the input circuit.

In the proposed DUT circuit due to the use of field effect transistors 2 and 3, this effect is significantly weakened, and the asymptotic attenuation at low frequencies is small due to the lack of transmission of changes in the source currents of transistors 2 and 3 to the gate circuit of transistor 3.

Thus, the claimed circuit design solution of the DUT is characterized by higher values of the gain K ₀ at the frequency of the quasi-resonance f ₀ , increased values of the Q factor Q, characterizing its selective properties, as well as a higher attenuation of the output signal in the low frequency range. This increases the efficiency of its use in measuring and radio devices for various purposes.

BIBLIOGRAPHIC LIST

1. Design of Bipolar Differential OpAmps with Unity Gain Bandwidth up to 23 GHz / N.Prokopenko, A. Budyakov, K.Schmalz, C.Scheytt, P. Ostrovskyy // Proceeding of the 4 ^th European Conference on Circuits and Systems for Communications - ECCSC'08 / - Politehnica University, Bucharest, Romania: July 10-11, 2008. - pp.50-53

2. Microwave SF blocks of communication systems based on fully differential operational amplifiers / Prokopenko NN, Budyakov A.S., K.Schmalz, S.Scheytt // Problems of developing promising micro- and nanoelectronic systems - 2010. Proceedings / under total ed. Academician of the Russian Academy of Sciences A.L. Stempkovsky. - M: IPPM RAS, 2010. - S.583-586

3. Patent US 4.843.343

4. Patent US 4,590,435, fig. 5

5. Patent US 4.999.585, fig. 2

6. Patent US 6.307.438, fig.2

7. Patent US 4.267.518, fig. 4

8. Patent WO 03052925

9. Patent application US 2008/0246538, fig. 3

10. Patent application US 2010/0201437.

Claims (1)

A measuring amplifier with a resonant amplitude-frequency characteristic, comprising an input signal source (1) connected to the base of the first (2) input transistor, a second (3) input transistor, the base of which is connected to the output (4) of the device, and the emitter is connected to the emitter of the first (2) the input transistor and through the first (5) current-stabilizing bipolar connected to the first (6) bus power supply, the current mirror (7), matched with the second (8) bus power supply, the output of which (9) through the second (10) current-stabilizing bipolar connected to the first (6) bus of the power source, the first (11) correction capacitor connected between the output (4) of the device and the common bus of the power sources (12), the second (13) correction capacitor, characterized in that field transistors are used as the first (2) and second (3) input transistors, the drain of which corresponds to the collector, the source to the emitter, and the gate to the base of the bipolar transistor, the drain of the second (3) input transistor is connected to the input (14) of the current mirror (7 ), the output (9) of the current mirror (7) is connected to the output of the device (4) through the second (13) correction capacitor, and the drain of the first (2) input transistor is connected to the second (8) bus of the power source, and the output of the device (4) shunted by alternating current with an additional resistor (15).

Images