JPH0548351A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To obtain the compact semiconductor integrated circuit with an excellent characteristic having an amplifier circuit to drive a frequency divider circuit and to obtain a high frequency output level, and ensuring isolation when having a high frequency oscillation circuit provided in one and same chip, with respect to the semiconductor integrated circuit used for a radio communication equipment. CONSTITUTION:An amplifier circuit 2 to convert one unbalanced output of a high frequency oscillation circuit 1 into two pairs of balanced outputs is provided in the integrated circuit. Amplifiers 3, 5 amplify the respective balanced outputs. The output of the amplifier circuit 3 being a balanced output is inputted to a frequency divider circuit 4. An output of the amplifier circuit 5 being an unbalanced output is amplified further by an amplifier circuit 6. Moreover, the amplifier circuit 5 as a balanced differential amplifier not employing a capacitor is formed in the semiconductor integrated circuit together with the high frequency oscillation circuit 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a structure of a semiconductor integrated circuit for radio communication, which has a built-in high frequency oscillation circuit.

[0002]

2. Description of the Related Art Conventionally, an unbalanced differential amplifier has been used as an amplifier circuit formed in an integrated circuit because of its good signal isolation and easy input / output with the outside when checking the operation of the circuit. A dynamic amplifier was used.

An example of a circuit constructed by using an unbalanced differential amplifier in an integrated circuit having a built-in high frequency oscillation circuit will be described below with reference to FIG. In FIG. 4, 1 is a high frequency oscillator circuit, 4 is a frequency dividing circuit, and 7, 8, 9, and 10 are amplifying circuits. Of these amplifier circuits, 7, 8 and 9 are unbalanced differential amplifiers, and one base of a pair of transistors forming the differential amplifier is grounded by a capacitor.

[0004]

However, in the above-mentioned structure, when the semiconductor integrated circuit is used, the grounded portion corresponds to the substrate, but elements such as transistors, capacitors and resistors are also connected to the substrate. There is a parasitic capacitance between them. The frequency of the carrier is, for example, VH
When the frequency becomes higher than the F band, the impedance of the inter-sub capacitance becomes low, and the high frequency signal easily flows through the substrate. In particular, when a high-frequency oscillation circuit is built in, the above-mentioned influence becomes large, and there is a problem that the isolation characteristic deteriorates.

The present invention solves the above problems, and an object thereof is to ensure isolation characteristics even for high frequency signals.

[0006]

In order to achieve the above object, the technical solution of the present invention is to use a balanced differential amplifier that does not use a capacitor as an amplifier that obtains all the gains of the amplifier circuit. The stages are connected by a balanced signal.

[0007]

According to the present invention, since the balanced type differential amplifier having the above-described structure eliminates the capacitor connecting the transistor and the substrate of the conventional unbalanced type differential amplifier and is connected by the balanced signal, the substrate is The coupling path with and is only the inter-sub capacitance parasitic in the element, and it is possible to reduce the influence of the high-frequency signal that flows from the high-frequency oscillation circuit to the differential amplifier and flows into the substrate. It is possible to reduce deterioration of characteristics.

[0008]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the first embodiment of the present invention. In FIG. 1, 1 is a high-frequency oscillator circuit,
2, 3, 5, and 6 are amplifier circuits, and 4 is a frequency dividing circuit.

The operation of the above arrangement will be described below. First, the high-frequency oscillation circuit 1 has an unbalanced output format in order to ensure noise characteristics, and the amplifier circuit 2 converts the unbalanced output signal into two pairs of balanced signals and supplies them to the amplifier circuit 3 and the amplifier circuit 5. Next, the amplifier circuit 3 buffer-amplifies the balanced output from the amplifier circuit 2 and drives the frequency dividing circuit 4. The other amplifier circuit 5 amplifies the balanced output from the amplifier circuit 2 to a required level and outputs it as an unbalanced output to the amplifier circuit 6, and the amplifier circuit 6 buffers and amplifies the output of the amplifier circuit 5. Performs high frequency unbalanced output.

FIG. 2 is a circuit diagram showing an example of a concrete implementation of the block diagram shown in FIG. The difference from the prior art is that the amplifier circuit 3 and the amplifier circuit 5 are configured by balanced differential amplifiers that do not use capacitors.

In the conventional unbalanced type, when the frequency of a signal becomes high frequency, the influence of inter-sub capacitance becomes large, and a high frequency signal circulates through the substrate together with a capacitor that grounds the transistor, and the isolation characteristic deteriorates. However, in this embodiment, all the amplifiers are of the balanced type that do not use capacitors,
Isolation characteristics are improved by reducing the coupling path with the substrate.

As is clear from the above description, according to this embodiment, the deterioration of the isolation characteristic for high frequency signals can be reduced as compared with the unbalanced differential amplifier.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a second embodiment of the present invention. The difference from the first embodiment is that a fifth amplification circuit is provided between the high frequency oscillation circuit 1 and the first amplification circuit 2. 7 is provided, and a PLL circuit is connected to the output of the frequency dividing circuit 4,
The point is that the control signal of the high-frequency oscillator circuit 1 can be obtained.

[0016]

As described above, according to the present invention, by using a balanced differential amplifier having two pairs of balanced output signals in an integrated circuit incorporating an oscillator, all amplifiers having gain are balanced differential type. It is possible to secure the signal isolation between the high frequency oscillation circuit and other circuits. Therefore, the high-performance of the high-frequency IC can be realized, and its industrial effect is large with respect to the downsizing and cost reduction of the device.

[Brief description of drawings]

FIG. 1 is a block connection diagram of a semiconductor integrated circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of an amplifier circuit section which is a main part in the first embodiment of the present invention.

FIG. 3 is a block connection diagram of a semiconductor integrated circuit according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of an amplifier circuit unit using a conventional unbalanced differential amplifier.

[Explanation of symbols]

 1 High Frequency Oscillation Circuit 2 1st Amplifier Circuit 3 2nd Amplifier Circuit 4 Divider Circuit 5 3rd Amplifier Circuit 6 4th Amplifier Circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasushi Higashida 4-3 Tsunashima Higashi 4-chome, Kohoku Ward, Yokohama City, Kanagawa Matsushita Communication Industrial Co., Ltd.

Claims (6)

[Claims] 1. A high-frequency oscillator circuit having an unbalanced output, and an unbalanced output of the high-frequency oscillator circuit having a first and a second output.
A first amplifier circuit for converting into a pair of balanced outputs;
A second amplifier circuit connected to the first balanced output of the amplifier circuit for obtaining a buffered amplified balanced output, a frequency divider circuit connected to the second amplifier circuit, and the first amplifier circuit. A third amplifier circuit connected to the second balanced output of the circuit for obtaining a buffer-amplified signal, and a fourth amplifier circuit for obtaining a high-frequency unbalanced output in the same chip. Integrated circuit. 2. The semiconductor integrated circuit according to claim 1, wherein the first and third amplifier circuits are balanced differential amplifier circuits. 3. The semiconductor integrated circuit according to claim 1, wherein the second amplifier circuit is composed of two emitter followers each having a balanced signal as an input, and obtains a pair of balanced outputs. 4. The semiconductor integrated circuit according to claim 1, wherein the fourth amplifier circuit comprises an emitter follower that receives an unbalanced signal and obtains an unbalanced output. 5. In addition to the circuit according to claim 1, a buffer comprising an emitter follower between the high frequency oscillator circuit and the first amplifier circuit, which receives the unbalanced output of the high frequency oscillator circuit as an input and obtains an unbalanced output. A semiconductor integrated circuit having an amplifier circuit. 6. The circuit according to claim 1 and a PLL circuit for forming a frequency synthesizer, which is connected to the frequency dividing circuit and obtains a control signal of the high frequency oscillation circuit, in the same chip. Semiconductor integrated circuit.