JPH046278Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to an output signal extraction circuit of an integrated circuit.

[Technical background of the invention]

Recent advances in semiconductor technology have led to the realization of semiconductor integrated circuits that incorporate many functional circuits on a single chip. Among these integrated circuits, there are various types, such as those for digital processing driven by a single clock frequency and those for analog processing that handle a plurality of signals having different frequencies.

FIG. 2 shows an audio signal processing section of a semiconductor integrated circuit in which an audio signal processing circuit and a video signal processing circuit are built into one chip. 1
1 and 12 are input terminals into which the audio FM intermediate frequency is input, and are connected to the limiter amplifier 13. The FM intermediate frequency signal output from the limiter amplifier 13 is passed through the active filter 14 to
The signal is input to the FM detector 15 and subjected to FM detection.
The FM detector 15 is connected to a detection tuning circuit 19 and a damping resistor 18 via pins 16 and 17. The FM detection output is input to the base of the output transistor Q1, and this transistor Q1
is led out from the emitter of the terminal via the terminal pin 20. The terminal pin 20 is input to a de-emphasis circuit 23 composed of a resistor 21 and a capacitor 22. In the above circuit, the block surrounded by the dash-dotted line is included in the integrated circuit.

[Problems with background technology]

The conventional output signal extraction circuit described above has the following problems. That is, in recent highly integrated circuits, the terminal pins are close to each other, and mutual interference occurs between the signals derived from the adjacent pins. In the above-mentioned audio signal processing circuit, since the integrated circuit itself has a wide band, the harmonic components are not sufficiently attenuated even after passing through the limiter stage and the detection stage, and appear up to pin 20. In the past, harmonic components led out to the outside did not pose much of a problem due to the wide spacing between pins, but due to high integration, harmonic components may be induced into other pins and cause interference between signals. A new problem has arisen:

[Purpose of invention]

This invention has been made in view of the above circumstances, and aims to provide an output signal extraction circuit for an integrated circuit that can prevent unnecessary components from being generated from terminal pins from which signals are output.

[Summary of the idea]

In order to achieve the above purpose, this invention
As shown in the figure, a de-emphasis circuit 43 (filter) to which the output of the output transistor Q11 is input is configured with an integrated resistor 40 and an external capacitor 42, and unnecessary harmonic components are removed from the integrated resistor. 40 to provide sufficient attenuation.

[Example of idea]

Examples of this invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of this invention, which is an example applied to an audio signal processing circuit. 31, 32
is an input terminal to which an audio FM intermediate frequency signal is input, and is connected to the limiter amplifier 33.
The FM intermediate frequency signal amplified to a constant level by the limiter amplifier 33 is passed through the active filter 34.
The signal is input to the FM detector 35 via the FM detector 35 and subjected to FM detection. The FM detector 35 has terminal pins 36 and 37.
A tuning circuit 38 for detection and a damping resistor 39 are connected via. The FM detection output, which is the output of the FM detector 35, is output from the output transistor Q1.
1 base. This output transistor Q11 constitutes an emitter follower circuit, and an output is taken out from its emitter, which is led out to a terminal pin 41 via a resistor 40 formed within the integrated circuit. Here, one end of a capacitor 42 that constitutes a de-emphasis circuit 43 together with the resistor 40 is connected to the terminal pin 41, and the other end of this capacitor 42 is connected to a reference ground potential terminal.

One embodiment of this invention is constructed as described above, and the blocks surrounded by the dashed line are integrated.

According to this invention, when the emitter output of the output transistor Q11 is taken out to the outside of the integrated circuit,
It is extracted through a de-emphasis circuit consisting of a resistor 40 and a capacitor 42, that is, a filter.
This filter is made up of a resistor 40 inside the integrated circuit and an external capacitor 42. Therefore, the harmonic components are sufficiently attenuated by the resistor 40 inside the integrated circuit and do not appear on the terminal pin 41. Therefore, there is no problem such as unnecessary harmonic components appearing on the terminal pin 41 and jumping into other adjacent terminal pins, as in the conventional case.
It can contribute to stable operation of integrated circuits and obtaining high quality signals.

Although the above explanation has been made using the audio signal processing section as an example, the present invention is not limited to this, and can be applied to the output side of various functional sections such as a phase detection output section, an amplified signal output section, etc.

[Effect of idea]

As mentioned above, according to this invention, unnecessary high-frequency components inside the integrated circuit that appear on the terminal pins are attenuated by forming a resistor that constitutes a filter within the integrated circuit, and It is possible to provide an output signal extraction circuit of an integrated circuit that can prevent unnecessary signals from being induced in the pins.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of this invention, and FIG. 2 is a circuit diagram showing a conventional output signal extraction circuit. Q11...Output transistor, 40...Resistor,
41...Terminal pin, 42...Capacitor, 43...De-emphasis circuit.

Claims (1)

[Claims for Utility Model Registration] (1) In an output circuit portion that derives a signal in the integrated circuit to the outside, an output transistor provided in the integrated circuit and an output transistor provided in the integrated circuit in order to amplify the processed signal in the integrated circuit. , an integrated resistor connecting between a signal output node of the output transistor and a terminal pin of the integrated circuit, and an integrated resistor having one end connected to the terminal pin and disposed outside the integrated circuit, forming a filter together with the integrated resistor. and a capacitor, and the integrated resistor of the filter is configured to attenuate unnecessary high-frequency components included in the output signal of the output transistor and prevent the unnecessary high-frequency components from appearing at the terminal pin. An output signal extraction circuit for an integrated circuit, characterized in that: (2) The output signal extraction circuit of an integrated circuit according to claim 1, wherein the filter is a de-emphasis circuit for audio signals.