JPH048667Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a variable phase circuit. In particular, the maximum control range in the delay direction and the advance direction when controlled can be set to approximately the same ratio, and it can be used in a voltage controlled oscillator. The present invention relates to a suitable variable phase circuit.

A circuit example of a variable phase circuit used in a conventional voltage controlled oscillator is as shown in FIG. It is composed of a differential amplifier 6 , a control input terminal 7, a bias 8, and an output terminal 9.

Here, the current signal at the intersection of the collectors of _the transistor Q ₂ which is a component of the first differential amplifier 3 and the transistor Q 4 which is a component of the second differential amplifier 4 is The signal appearing at the base of transistor _Q1 , which is a component of
The phase is shifted by the phase shift circuit 5 , and the first and second
The signal appearing at the base of the transistor Q ₂ Q ₃ , which is a constituent element of the differential amplifiers 3 and 4 , is denoted by B, the first and second
Transistors used as constituent elements of differential amplifiers 3 and 4
If the emitter differential resistances of Q ₁ Q ₂ and transistor Q ₃ Q ₄ are γe ₁ and γe ₂ , then (B-A)/γe ₁ -B/γe ₂ is obtained.

Next, when the transistors Q ₅ and Q ₆ , which are the constituent elements of the third differential amplifier 6 , are balanced, the emitter differential resistances γe ₁ and γe ₂ of the transistors Q ₁ Q ₂ and Q ₃ Q ₄ are the same. Figure 2a shows the composite current appearing in the collector of the transistor Q ₂ Q ₄ which is a constituent element of the first and second differential amplifiers 3 and 4 .
The variable range of the composite current phase appearing at the collectors of Q ₂ and Q ₄ is from B-A to -B with -A as the center.

When converting the circuit shown in Figure 1 into an IC, if you want to configure a voltage-controlled oscillator with a relatively low frequency, the resistance R in the phase circuit cannot be made too large in order to stabilize the bias of the differential amplifier. A drawback arises in that the value of the capacitor C in the circuit must be increased, and when the capacitor is integrated into an IC, this leads to an increase in the pellet area of the IC, which is a problem. Therefore, for example, if the amount of phase shift of B is made small, the variable range becomes unbalanced around -A as shown in FIG. 2b, which is a problem.

The present invention eliminates the above-mentioned drawbacks, and an embodiment of the present invention shown in FIG. 3 will be described below with reference to the drawings. In the explanation, parts corresponding to those in FIG. 1 will be given the same figure numbers. That is, in the circuit of FIG. 1, the base of the transistor Q ₁ , which is a component of the first differential amplifier 3 , is connected to the base of the transistor Q 4 , which is a component of the second differential amplifier ₄ .
A resistor 10 is connected to the base of the bias resistor 8, and the resistor is set to have the same value as the bias resistor 8, for example. Then, the structure of the second differential amplifier 4 is changed by the bias resistor 8 and the resistor 10 provided between the bias resistor 8 and the base of the transistor Q ₁ which is a component of the first differential amplifier 3 . Transistor Q ₄ which is an element
A base signal of 1/2A appears at the base of.
The current signal at the intersection of the collectors of transistors Q ₂ and Q ₄ , which are the constituent elements of the first and second differential amplifiers 3 and 4 , is B- centered around (B-A)-B+1/2A=-1/2A. A variable range from A to 1/2A-B (θ=about ±60° in FIG. 4) can be obtained.
The current signal at the intersection of the collectors of transistors Q ₂ and Q ₄ is illustrated in FIG. 4.

Incidentally, in the explanation of FIG. 3, the case where the resistance values of the resistor 10 and the bias resistor 8 are equal was explained, but this is determined depending on the amount of phase shift of the phase shift circuit 5 , and for example, as shown in FIG. If the amount of phase shift is smaller than the case, the value of the bias resistor 8 may be set larger than the value of the resistor 10 accordingly.

In the embodiment shown in FIG. 3, a case has been described in which the variable phase circuit of the present invention is used in a voltage controlled oscillation circuit, but the present invention is not limited to this, and instead of the resonant circuit 2 , a resistor etc. It can also be used as a normal phase shift circuit by using a load.

As described above, in the present invention, phase shifting is achieved by connecting a resistor between the base of one transistor of the first differential amplifier and the bias resistor of one transistor of the second differential amplifier. This has the advantage that a sufficient phase variable range can be obtained even when the amount of phase shift of the signal phase-shifted via the circuit is small.

Furthermore, differential bias can be stabilized even when the frequency is relatively low, and for this reason, the phase shift circuit can be built into the IC and the number of pins can be reduced.

[Brief explanation of drawings]

FIG. 1 shows an example of a conventional variable phase circuit used in a voltage controlled oscillator, and FIGS. 2a and 2b show collectors of one transistor in each of the first and second differential amplifiers in FIG. Figure 3 shows an example of the variable phase circuit used in the voltage controlled oscillator of the present invention, and Figure 4 shows the composite current vector diagram that appears at the intersection.
FIG. 6 shows a composite current vector diagram appearing at the common collector of one transistor of each of the first and second differential amplifiers shown in the figure. Explanation of main figure numbers, 1...Power terminal, 2 ...Resonant circuit, 3 ...First differential amplifier, 4 ...Second differential amplifier, 5 ...Phase shift circuit, 6 ...Third difference dynamic amplifier,
7... Control input terminal, 8... Bias resistor, 9...
...output terminal, 10...resistance.

Claims (1)

[Scope of utility model registration request] a first differential amplifier comprising first and second transistors whose emitters are commonly connected, an input signal being applied to the base of the first transistor; and a third differential amplifier whose base is connected to the base of the second transistor. a second differential amplifier comprising a transistor and a fourth transistor whose emitter is connected to the emitter of the third transistor; and a second differential amplifier connected between the base of the first transistor and the common base of the second and third transistors. a phase shift circuit, a reference voltage source that applies a bias to the base of the fourth transistor via a bias resistor, a power supply connected to a common collector of the first and third transistors, and the first and second differential transistors; between the base of the first transistor and the base of the fourth transistor in a variable phase circuit comprising a third differential amplifier that changes the phase of the output signal by controlling the shunt ratio of the current flowing to the common emitter of the amplifier. A phase shift control resistor is provided in the phase shift circuit, and the bias resistor and the phase shift control resistor are connected in accordance with the amount of phase shift of the phase shift circuit so that the phase shift change range of the output signal is equal in the lead range and the delay range. A variable phase circuit characterized in that a resistance ratio is set and a phase-shifted output signal is derived from a common collector of the second and fourth transistors.