JP2596136B2 - Current control type phase shift circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current control type phase shift circuit that arbitrarily controls a phase shift amount of an output signal with respect to an input signal.

2. Description of the Related Art FIG. 4 shows a phase shift circuit using an operational amplifier well known in the related art. In the figure, the non-inverting input of the operational amplifier 1 (+) in through the differentiating circuit due to the capacitance C ₁ and the resistance R ₁ (time constant circuit) provides an input signal, the input and output terminal of the operational amplifier 1 terminal 2 And an inverting input terminal (-) is connected to an intermediate connection point between the resistors r and r connected in series between the resistors r and r to invert and amplify with a gain of 1. In this conventional circuit, the phase shift amount 入 力 of the input signal with respect to the output signal at the input signal frequency f is expressed by the following equation.

ψ = −tan ⁻¹ (f / f ₀ ) (1) where f ₀ = 1 / (2πC ₁ R ₁ ) Then, the value of the resistor R ₁ or the value of the capacitor C ₁ is varied to shift the phase. ψ was variable.

SUMMARY OF THE INVENTION However, in the case of varying the resistance value of the resistor R ₁ in the conventional circuit configuration, as the resistance R _1, unless employs a variable resistor or MOS resistance, the adjustment of the resistance value was difficult . Capacity C ₁
Is variable, it is difficult to adjust a large value unless variable capacitance is adopted. Also, since the variable resistor and the variable capacitance are mechanically adjusted, they are not suitable for electronic adjustment, and there is a drawback that an electronically variable MOS resistor cannot be made by a bipolar process. And a process that mixes bipolar. But,
Then, it had a drawback that it would increase the cost.

The present invention eliminates such inconveniences.
An object of the present invention is to provide a current control type phase shift circuit which can electronically arbitrarily change a phase shift amount without using a special component such as a resistor.

Means for Solving the Problems A current-controlled phase shift circuit according to the present invention is configured such that an emitter is coupled to a differential pair transistor whose base input is supplied with an input signal, and forward conduction is performed to one collector of the differential pair transistor. Diode means connected as follows:
It comprises a capacitor connected in parallel with the diode means and a current source for varying the emitter current of the differential pair transistor, and takes out an output signal from a terminal of the capacitor.

With the above configuration, when the current value of the current source is varied, the differential resistance of the diode means changes in inverse proportion to the current value,
The phase shift amount of the output signal with respect to the input signal can be arbitrarily varied.

Embodiment Hereinafter, a current control type phase shift circuit of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of a current control type phase shift circuit according to the present invention. In this figure, Q ₁ and Q ₂ are transistors that combine emitters to form a differential amplifier, and V ₂ is a transistor. DC voltage source that applies a DC bias to the bases of transistors Q ₁ and Q ₂ , V ₁ is an input signal source, Q ₃ and Q ₄ are transistors, C ₂ is a capacitor, I ₁ is a variable current source, and I ₂ is a constant current source , A is an output terminal, and Vcc is a power supply terminal. The transistor Q ₄ having the emitter connected to the constant current source I ₂ forms an emitter follower circuit, receives the terminal voltage of the capacitor C ₂ with high impedance, and outputs the output signal to the output terminal A with low impedance. .

Next, the operation of the phase shift circuit shown in FIG. 1 will be described. Diode means (diode connected transistor) Q ₃ is always used in a state of conducting forward, it serves as a load of the differential amplifier (Q _1, Q _2). Then, the emitter current I _E3 of the transistor Q ₃ and the saturation current are represented by I
s, the base-emitter voltage V _BE3, electron charge amount q, the Boltzmann constant K, when the absolute temperature is T, the emitter current I _E3 of the transistor Q ₃ are expressed by the following equation.

AC impedance of _{I E3 = Isexp (q / KT} ) V BE3 ...... (2) diode means, a (2)
By differentiating with I _E3 , the differential resistance is obtained as re _3. If the thermal voltage V _T = KT / q, the following equation is obtained.

re ₃ = dV _BE3 / dI _E3 = V _T / I _E3 (3) That is, the resistance value changes depending on the magnitude of the emitter current I _E3 , and a parallel circuit of the diode means Q ₃ and the capacitor C _2. Is the cutoff frequency f ₀ depending on the magnitude of the emitter current _IE3.
Low-pass filter circuit (hereinafter referred to as LPF)
Is configured. The transfer function H (jω) of the first-order LPF can be expressed by the following equation, where ω is the input angular frequency, ω ₀ is the input angular frequency to be cut off, and f is the input frequency.

H (jω) = 1 / (1 + jω / ω ₀ ) (4) When H (jω) is displayed in polar coordinates, it can be expressed by the following equation.

H (jω) = | H ( jω) | e jφ ...... (5) Then, tanψ = -ω / ω _0, and the phase difference ψ can be expressed by the following equation.

φ = −tan ⁻¹ (f / f ₀ ) (6) Furthermore, the cutoff frequency f ₀ is f ₀ = 1 / (2π · C ₂ · re
Obtained in _3), since the emitter current I _E3 diode means Q ₃ are a half of the current of the variable current source I _1, f ₀ = ₁ / _{[2π · C 2 · (2V T} / I 1) ] = I ₁ / (4π · C ₂ · V _T ) (7) As can be seen from the above equations (6) and (7),
Depending on the current value of the variable current source I _1, optionally variable in the phase difference φ between the input signal and the output signal.

Next, another embodiment shown in FIG. 2 will be described. This embodiment is a phase shift circuit for obtaining a rectangular wave output signal from a sine wave input signal, and is an example in which the output signal is used for digital signal processing.

In FIG. 2, transistors Q ₅ and Q ₆ of a differential pair constitute a differential amplifier, each base is provided with a DC bias of a DC voltage source V ₄ , and a base of the transistor Q ₅ is provided with an input signal source V The signal of ₃ is input. In addition, transistors
Connect the diode means (diode connected transistor) Q ₇ to the forward conduction to the collector of Q _6, by connecting a capacitor C ₃ in parallel with the diode means, constituting the phase shift circuit. This circuit, by a variable current value of the variable current source I _3, changing the differential resistance of the diode means Q _7, and controls the phase shift amount.

Next, the bases of the transistors Q ₉ and Q ₁₀ of the differential pair are DC-biased by the DC voltage source V ₄ , and a variable current source is
Give the current of I ₄ and apply the current of this variable current source I ₄ to the variable current source
In conjunction with the I ₃ to variable. Then, the transistor Q of the connected diode connected to the collector of the transistor Q _9
11 generates a diode voltage corresponding to the DC voltage component between the terminals of the diode means Q ₇ described above (average voltage) between terminals.

When the current values of the variable current sources I ₃ and I ₄ are varied in conjunction with each other,
A DC voltage component of the base-emitter voltage V _BE7 of the diode means Q _7, and a terminal voltage of the transistor Q _11, the same size, yet it can be varied in the same amount of change.
Then, the transistor that constitutes the emitter follower circuit
A voltage comparator for comparing the emitter potential of the _{Q 8, Q 12 (Q 13} ~
Q ₁₅₎ is when to vary by changing the phase shift amount of the current value of the variable current source I _3, and the reference potential and the phase shift that varies in accordance with the variation of the DC voltage generated between terminals of the diode means Q ₇ signal And performs a waveform shaping operation to output a phase-shifted rectangular wave.

Figure 3 is shows the operation waveforms of the phase shift circuit of FIG. 2, the variable current source I ₃ and the variable current source I ₄ while keeping the relationship I ₃ = I _4, the variable current source I ₃ current for explaining the operation when lowered from the level of I _3-1 to the level of I _3-2. (1) in FIG. 3 shows the voltage waveform of the input signal V _1, (2) the I _3-1
Shows the waveforms of the output voltage V _B1 of the output terminal _B and the output voltage V _C1 of the output terminal C when the current is applied, and (4) shows the voltage waveform of the output voltage V _D1 of the output terminal D at that time. . (3) shows the voltage waveform of the output voltage V _B2 of the output terminal _B and the output voltage V _C2 of the output terminal C when the level is lowered to the level of I _3-2 , and (5) shows the output terminal at that time 3 shows a voltage waveform of an output voltage V _D2 of D.

When the current of the variable current source I ₃ of FIG. 2 to a variable, the differential resistance of the diode means Q ₇ is varies depending on the magnitude of the current I _3, therewith also change the DC diode voltage simultaneously. However, since the current I ₄ is varied in conjunction with the current I ₃ , the third
As shown in FIG. 2B, the voltage V _B1 at the output terminal B is output so as to oscillate around the DC voltage V _C1 at the output terminal C. A voltage comparator for comparing the voltage waveform V _C1 and V _B1 (Q ₁₃ ~Q
_15), and the V _C1 and V _B1 outputs an output voltage V _D1 converted into a rectangular wave at the point of intersection. Then, the current of the variable current source I ₃ is
Reducing the level of _3-2, the differential resistance of the diode means Q ₇ is increased, the phase shifts as [Delta] [phi, the diode voltage of diode means Q ₇ is reduced, the DC potential of the output terminal B (average voltage) is To rise. Accordingly, the smaller the base-emitter voltage of the transistor Q _11, increases the DC voltage V _C2 of the output terminal C by the same level as the output terminal B, and V _B2 and V _C2 shown in FIG. 3 (3) And the rectangular wave output V whose phase is shifted by Δφ
_D2 ((5) in FIG. 3) is output to the output terminal D.

As described above, when the current value of the current source is varied, the differential resistance of the diode means changes in inverse proportion to the current value, and the phase of the output signal with respect to the input signal changes. This provides a special effect that the shift amount can be arbitrarily changed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of a current control type phase shift circuit of the present invention, FIG. 2 is a circuit diagram of another embodiment of the present invention, and FIG. 3 is a diagram of the embodiment of FIG. FIG. 4 is a diagram for explaining the operation, and FIG. 4 is a circuit configuration diagram of a conventional phase shift circuit. Q ₁ ~Q ₄ ...... transistor, C ₂ ...... _{capacity, I 1, I 3, I} 4 ...... variable current source, I ₂ ...... constant current source, V _1, V ₃ ...... input signal source, V ₂ ,
V ₄ ...... DC voltage source, A, B, C, D ...... output terminal, R ₂ ...... resistors, Vcc ...... power terminal.

Claims (1)

(57) [Claims] A differential pair transistor having an emitter coupled thereto and an input signal supplied to a base input; diode means connected to one collector of the differential pair transistor so as to conduct in a forward direction; A current-controlled phase shift circuit comprising: a capacitor connected in parallel; and a current source for varying an emitter current of the differential pair transistor, and extracting an output signal from a terminal of the capacitor.