JPS5927612A - Amplifying circuit - Google Patents

Abstract

PURPOSE:To attain stably a broad band, by providing an impedance adjusting circuit utilizing a differentiating resistor of a diode so as to adjust externally the peaking characteristics or the tuning characteristics. CONSTITUTION:A series feedback amplifying circuit having an input terminal 2 and an output terminal 4 is formed with an input transistor 6, a load resistor 7 and a series feedback resistor 8. Further, the impedance adjusting circuit 41 comprising a diode 22, a capacitor 9, and a constant current source 17 is connected between a high potential power supply terminal 1 and a low power supply terminal 2. The impedance of the adjusting circuit 41 is changed by a signal at a terminal 23. Since the gain of this amplifying circuit is expressed approximately with equation, the peaking characteristics are made variable by the signal at the terminal 23.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier circuit having peaking characteristics or tuning characteristics that is used for widening the band in monolithic integrated circuits, hybrid integrated circuit technologies, etc. in which it is difficult to modify or adjust the element values of circuit components. It is related to.

The prior art will be explained by taking a peaking type amplifier circuit as an example. FIG. 1 shows a conventional emitter beaking amplifier circuit. The circuit configuration consists of a human quadrant and a load resistance of 7.
(R'LI) + series feedback resistor 8CRp:1) and peaking gJt9 (Cp), 3I'i input terminal,
4 is an output terminal. This amplifier circuit is a series feedback type amplifier circuit, and the parallel connection of the series feedback resistor 8 (REI) and the peaking capacitor nt9 (Cp) makes the amount of feedback large in the low frequency region and small in the high frequency region. The voltage gain Av is approximated by ω being the angular frequency and ωb being the 3 dB lower band of the amplifier circuit when the Beekinog Answer 9 (Cp) is not connected.

Therefore, ω = 1 / (REI −Cp
), a zero point occurs when the series feedback resistor 8 (
By setting the peaking capacitance 9 (REI) and the peaking capacitance 9 (Cp) to appropriate values, it is possible to compensate for the band narrowing effect of the input quadrant transistor itself, and it is possible to widen the band of the amplifier circuit.

FIG. 2 shows a conventional differential emitter peaking amplifier circuit. FIG. 2 will be explained. The circuit configuration is a differential type of the emitter peaking type amplifier circuit shown in FIG. Load resistance 7 (RLI) I Load resistance 15 (RL
2) 1 series feedback resistor 8 (Rp:+).

A differential pair is formed by the series feedback resistor 16 (RE2), a constant loop, and a wave circuit 17, and the input quadrant transistor and the input quadrant are connected (16 configurations.
1 and 3-2, and the output terminals are 4-1 and 4-2.
It is. The operation of this amplifier circuit is considered to be similar to the emitter peaking type amplifier circuit shown in FIG. is approximated by 16 (Rh; 2) or equal.

Therefore, one series feedback resistor 8 (R, ρ.

16 (RE2) and Hihikino f'gM9 (Cp)k!
By setting H+ff, it is possible to perform peaking that improves the overall frequency characteristics.

As explained above, the peaking technique is an effective technique for widening the band of an amplifier circuit. However, when peaking is used in integrated circuits and the like, there is a limit to the accuracy of resistance and capacitance values, making it difficult to obtain peaking characteristics as designed. Especially for peaking in the high frequency range, it is necessary to keep the product of the series feedback resistance and peaking capacitance small, but it is difficult to achieve low resistance and low capacitance values with high precision, and in some cases, it may cause inconveniences such as excavation. This makes it difficult to perform peaking as designed. Also,
As shown in equations (1) and (2), the peaking pole is the product of CP and REI. Since the REIO value is determined from the gain and DC design, the adjustment of the amount of peaking depends only on Cp. If you increase Cp in order to apply more peaking, the pole will shift to the lower frequency 111. This results in an undesirable result in which the gain is increased on the low frequency side. If an attempt is made to avoid this, there is a problem that peaking cannot be applied sufficiently and it is difficult to effectively utilize peaking to achieve a wide band.

Although the explanation has been given using a beaking amplifier circuit as an example, a general tuned amplifier circuit is also similar and has similar problems.

In order to eliminate these glue points, the present invention includes an innovation adjustment circuit that uses diode differential resistance that is easy to integrate. The present invention proposes an amplifier circuit that is characterized by independently controllable components, and can achieve stable broadband operation, easy manufacturing, and low cost.

The following is a detailed explanation of the present invention.

FIG. 3 shows an embodiment of the basic innovidance adjustment circuit of the present invention, where ■ is a high potential power supply terminal, 2 is a low potential power supply terminal, 21il-i signal input terminal, and 23 is an impedance adjustment input terminal. , 9 is a droplet, 22 is a diode, and 17 is a source. Further, FIG. 3 +bl is an AC equivalent circuit of the circuit in FIG. 3 +al for explaining the operation, and CD is the diffusion capacitance jt of the diode 22.
, Rp is the differential resistance of the diode 22. In the tb1 diagram, the impedance between the terminal 21 and the low potential power supply terminal 2 can be expressed by the following equation.

The product of RD and CD is a value determined by the cutoff frequency of the diode and is always constant regardless of the operating current ID, so the frequency characteristic of the impedance in equation (3) is as shown in Figure 4. That is, the pole ω1 determined by O and RD-CD. ω3
and has a zero point ω2 determined by RD (Cp + Co).

Extreme ω1. ω2 is constant regardless of the operating current ID of the diode 22, and the zero point ω2 is determined by appropriately selecting CP.
By adjusting ID and adding RD, two poles ω1
It can be freely changed between °ω3. Therefore, the frequency characteristic of the impedance can be made partially flat as shown in FIG. 4, and its region can be freely set. Adjustment of Cp is difficult when this circuit is implemented using an integrated circuit, but adjustment of RD, that is, adjustment of ID, can be easily performed from an external terminal.

The circuit shown in FIG. 3 +al can be affected by an earthquake as shown in (C).

Figures 5 and 6 show the remarkable features of this circuit, and show the frequency characteristics of Innovidance when a resistor RE is connected in parallel. The figure shows the capacitance CP as a parameter. In the figure, the resistor R is 80Ω, and the diode transit time τ is 25 pS. FIG. 5 shows that the impedance l of the flat part can be adjusted independently by the current ID, and even if the ID is changed, the point where the impedance starts to decrease, that is, the pole, hardly changes. On the other hand, FIG. 6 shows that the point at which the impedance begins to decrease independently of itself and the poles can be adjusted, and the magnitude of the impedance at the flat portion does not change even if the CP is changed. In this way, the impedance can be freely changed and has a flat part, and the ability to arbitrarily adjust the impedance of the flat part using the 11L ID is especially useful for realizing peaking amplifiers. It's very difficult for KuI.

FIG. 7 shows an embodiment of the present invention of a peaking amplifier circuit.

The circuit configuration is input quadrant transistor, load resistance 7 (RLI
) A series feedback type amplifier circuit is formed by + series feedback resistor 8 (REI), 3 is an input signal terminal, 4 is an output signal terminal, 2 is a low potential power supply terminal, and 41 is an impedance adjustment circuit. In this amplifier circuit, the gain can be approximately expressed by the following equation.

L "" REI/Z Zd This is the impedance of the inopedance adjustment circuit shown in FIG. 3. As explained above, the denominator REI and the parallel impedance 2 have the frequency characteristics shown in FIGS. 5 and 6. Therefore, the frequency characteristic of the gain G is in the form of a reciprocal of the impedance of the molecule υ, and has a peaking quantity characteristic. This l characteristic is shown in Figure 5, #! As explained in Figure 6, by setting Cp, the frequency at which peaking starts can be set independently of the DC bias characteristics, etc., and the amount of peaking can be set independently of the current ID.
Depending on the cocurrent bias characteristics, the peaking start frequency can be freely adjusted independently.

FIG. 8 shows another embodiment of the peaking amplifier circuit of the present invention, where ■ is a high potential power supply terminal A, 2 is a low potential power supply terminal, and 3-1 is a low potential power supply terminal.
and 3-2 is signal human power y; 1 shiko, 4-1 and 4-
2 is a signal output terminal, 7 is a negative I'=4r resistor, 8 is a series feedback resistor, 41 is an impedance adjustment circuit, and 23 is an innovidance adjustment terminal A. In this amplifier circuit, the same principle as in the amplifier circuit shown in FIG. 5 is used to select the peaking characteristic of Cp and to obtain one output from the external terminal. It can be freely adjusted by controlling I.

As Shigeko explained, the present invention utilizes the differential resistance of a capacitor and a diode, and by controlling the current bias conditions of the diode, the impedance can be adjusted and changed. In particular, when using a peaking amplifier circuit, the peaking start frequency and the peak/high frequency can be adjusted and set independently. In other words, the capacitor value can be set from the desired peaking start point, and the amount of peaking can be easily adjusted from an external terminal. I can do it. Therefore, in 4), even if it is difficult to modify element values such as an integrated circuit, the peaking amount can be adjusted while checking the characteristics, and stable amplifier characteristics can be achieved with high precision. This has the advantage of improving yield, lowering costs, and maximizing the bandwidth. Not only the peaking amplifier circuit, but also the tuned 12+1 amplifier circuit, which has a specific frequency characteristic, can have its frequency characteristics adjusted from the external ψ; There is.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional emitter beaking amplifier circuit, Fig. 2 is a circuit diagram showing an example of an Ii differential type emitter beaking amplification circuit, and Fig. 3 is an example of an impedance adjustment circuit used in the present invention.・The circuit diagram shown in Figure 4 is a diagram for explaining the operating principle of the impedance adjustment circuit, Figures 5 and 6.
The figure is a characteristic diagram showing an example of the frequency characteristics of the peaking adjustment circuit and the impedance of the il+2 column of resistors, and Figures 7 and 8 show examples of the peaking adjustment type amplifier circuit of the present invention.
＜This is a circuit diagram.
4.4-1.4-2...Signal output terminal, 6,
DESCRIPTION OF SYMBOLS 10... Input transistor, 7.15... Load resistance, 8, 16... Series feedback resistance, 9... Peaking capacity, 17... Constant current circuit, 21... Signal input terminal, 22 ...Diode, 23... Impedance adjustment input terminal 1.41... Impedance adjustment circuit. For patent purposes, ``1 representative of Telegraph and Telephone Public Corporation (1 person outside fi.
Figure 3 J” (a) (b) (C) Figure 4

Claims (2)

[Claims] (1) Consists of a diode having an anode terminal and a cathode terminal, a current source whose current value is controllable and which has a current value control terminal, a current output terminal, and a common ground terminal, and a capacitor having two terminals. An anode terminal is connected to a high potential power source, a cathode terminal of the diode is connected to a first terminal of the capacitor and an output terminal of a current source, and a current value control terminal of the current source is adjusted to 1. An amplifier circuit comprising an impedance adjustment circuit capable of adjusting impedance between a second terminal and a ground potential. (2) consisting of a diode having an anode terminal and a cathode terminal, a current source whose current value is controllable and having a current value control terminal, a current output terminal, and a common ground terminal, and a capacitor having two terminals; The cathode terminal of the diode is connected to a low potential power supply, and the anode terminal of the diode is connected to the first terminal of the capacitor and the output terminal of the current source, and the current value control terminal of the current source is adjusted to 1. An amplifier circuit comprising an impedance adjustment circuit capable of adjusting an impedance between a second terminal of the amplifier and a ground potential.