JPS5822139Y2 - phase comparator - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to improving a phase comparator, and in particular, improving characteristics by equalizing the bias level of an input signal applied to the phase comparator and a reference signal with which the input signal is compared. The present invention aims to provide a phase comparator suitable for integrated circuit implementation.

A phase comparator is known that compares the phases of an input signal and a reference signal and obtains a DC output signal according to the phase difference.

Such a phase comparator usually has a preamplifier at the front stage to amplify the input signal, but the level difference between the DC component in the preamplifier output signal and the DC component included in the reference signal is large. As a result, various adverse effects occur.

For example, when the phase comparator is used in a PLL (phase locked loop), if the level difference is large, a capacitor for smoothing the output signal of the phase comparator must be used as a capacitor. This has the disadvantage that the ripple causes malfunction of the VCO (voltage controlled oscillator).

In order to improve the drawbacks caused by the level difference, it is also known that a capacitor is inserted between the output terminal of the preamplifier and the input terminal of the phase comparator circuit.

However, in such a phase comparator, a new disadvantage of phase rotation arises, which is undesirable.

The present invention has been developed in view of the above points, and will be described below based on embodiments with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which 1 a preamplifier for amplifying an input signal applied to a power terminal 2;
”The output signal of the preamplifier 1 and the reference signal generation circuit 4
A phase comparison circuit for comparing the phase with the output signal from the
5 is a capacitor for removing high frequency components from the output signal of the phase comparison circuit 1p, l is a differential amplifier circuit for amplifying the main output DC signal of the phase comparison circuit, and 7 is a supply of DC bias to the preamplifier 1. A bias circuit 8 is a buffer amplifier having substantially the same output characteristics as the preamplifier.

Therefore, the phase comparator circuit 3 includes four resistors 9.10
, 11 and 12 and a pair of switching transistors 13
and 14, and the output reference signal from the reference signal generation circuit 4 is applied to the bases of the pair of switching transistors 3 and 14.

In addition, the round blade characteristics of the buffer amplifier 8 are made to be approximately the same as the input/output characteristics of the preamplifier 1, so that they are affected by the same circuit configuration, and are also approximately the same in terms of temperature characteristics, etc.
The semiconductor integrated circuit board is disposed in close proximity to the semiconductor integrated circuit board.

Next, the operation will be explained.

The phase comparator circuit 1 is a kind of multiplication circuit that multiplies the input signal applied to the signal scale point A by the reference signal applied to the points B and C from the pair of switching transistors 3 and 14.

Now, let the input signal Sin applied to input point A be S =
A[F]in(ωt+θ) ・・・・・・・・・
1 (where ω is the angular velocity, θ.

is the phase and A is the amplitude), and the reference signal S applied to point H is S = Bco
s(ωt+θ) 2 (where θ1 represents the phase and B represents the amplitude.

), and the reference signal S applied to point C is 5=-Bc
If os(ωt+θ) ......3, then the signal S1 applied to the base of one transistor 15 of the four differential amplifier circuits 6 is S = ABsin(θ - θ) ...・・・
...4, and the signal S applied to the base of the other transistor 16 is S = ABsin(θ-θ) ......
...It becomes 5.

Therefore, if the phase of the input signal and the phase of the reference signal match, 51-o, S220, and if there is a phase difference, the signal applied to the bases of the pair of transistors 15 and 16. The thickness of is a value corresponding to the phase difference.

Note that high frequency components other than those shown in the fourth and fifth equations are removed by the capacitor 5 and are not transmitted to the differential amplifier circuit 6.
It is arranged to amplify the image (Fig. A).

The preamplifier 1 receives a DC bias from a bias circuit 7 in order to perform class A amplification.

Therefore, the output signal of the preamplifier 1 (signal applied to point A) becomes as shown in FIG.

On the other hand, the input terminal of the buffer amplifier 8 is connected to the bias circuit γ
connected only to

Therefore, the output signal of the buffer amplifier 8 is as shown in FIG.
Nojo<naru.

The preamplifier 1 and the buffer amplifier 8 are arranged close to each other on the integrated circuit board and have the same circuit configuration.

Therefore, the output characteristics are approximately the same, and the temperature characteristics and the like are also approximately the same.

Therefore, the level of the bias signal applied to point A and point B
is approximately equal to the level of the bias signal applied to
The conventional drawbacks are improved.

As mentioned above, since there is no adverse effect caused by the DC signal (bias signal), the phase comparator circuit of the phase comparator according to the present invention can be directly connected to the preamplifier, and therefore has the advantage that it can be easily integrated into an integrated circuit. .

In addition, since it can be directly connected, there are no adverse effects such as phase rotation, and P
It is a practical device that has various advantages such as not causing malfunction even when used in LL.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a phase comparator according to the present invention, and FIG. 2 is a characteristic diagram showing waveforms of various parts in FIG. 1. Explanation of main drawing numbers, 1...Preamplifier, 3...
... Phase comparison circuit, 7 ... Bias circuit, 8
...Buffer amplifier.

Claims (1)

[Scope of utility model registration request] a preamplifier that amplifies an input signal; a phase comparison circuit that compares the output signal of the preamplifier with a reference signal from a reference signal generation circuit and generates an output signal according to the phase difference;
a buffer amplifier having substantially the same characteristics as the preamplifier and to which a DC bias equal to the DC bias applied to the preamplifier is applied as an input signal, and connecting the preamplifier and the phase comparison circuit with DC connection;
A phase comparator characterized in that the output signal of the buffer amplifier is applied as a bias signal to the reference signal generation circuit in order to make the DC level of the reference signal substantially equal to the DC level of the output signal of the preamplifier.