JPH03250454A - Semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To reduce noise generated at the time of switching a reproducing signal for a minimum holding time by delaying a switching signal by a delay circuit based upon the delay time of a BPF. CONSTITUTION:The delay circuit 9 changes the delay time by the frequency of a lock signal e.g. inputted from a control signal input terminal 8 to delay a switching signal supplied from an input terminal 4 and supply the delayed signal to a sampling/holding signal generating circuit 10. Thereby, the circuit 10 supplies a sampling/holding signal with the same pulse width as a certain period of a noise to a sampling and holding circuit 7, which holds the prescribed part of a voice signal only by the minimum in accordance with the certain period of the noise and outputs a highly accurately signal whose noise is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor integrated circuit device suitable for application to, for example, a VTR playback device.

[Summary of the invention]

The present invention relates to a semiconductor integrated circuit device that is suitable for application to, for example, a VTR playback device, and includes a bandpass filter to which an output signal from a changeover switch is supplied, and a demodulation circuit that demodulates the output signal from the bandpass filter. , a sample hold circuit that holds a predetermined portion of the demodulated output signal from the demodulation circuit, and a sample hold signal generation circuit that supplies a predetermined sample hold signal to the sample hold circuit based on a switching signal that switches the changeover switch. In a semiconductor integrated circuit device having
By providing a delay circuit that delays the switching signal based on the delay time of the bandpass filter, it has a simple configuration, eliminates the need for adjustment, and reduces the noise generated when switching the playback signal with the minimum hold time. , which can output highly accurate signals.

[Prior Art] Conventionally, a semiconductor integrated circuit device as shown in FIG. 2 has been used, for example, in a VTR playback device.

In FIG. 2, (1a) and (Ib) indicate magnetic heads arranged on a rotating drum at 180 degrees opposite positions, and these magnetic spatulas (1a) and (1b) are used to record information on a magnetic tape. recording signals recorded alternately on the tape so as to form inclined tracks in the longitudinal direction of the tape;
That is, a signal in which a pilot signal, a video signal, and an audio signal are multiplexed and recorded is alternately reproduced as shown in FIG. 3A.

The multiplexed signals A and B reproduced by the magnetic heads (1a) and (1b) are passed through amplifiers (2a) and (2b) to the respective fixed contacts (3a) and (3) of the switch (3).
b) are alternately supplied to each. The movable contact (3c) of this switch (3) is connected to the fixed contact (3a) by a switching signal as shown in FIG.
and (3b), and are connected alternately to the bandpass filter (5) having a passband of 1.5 MH2 and the video signal processing system. The signals are respectively supplied.

Then, this bandpass filter (5) extracts an audio signal as shown in FIG.
The signal is supplied to a sample and hold circuit (7).

The sample and hold circuit (7) converts the audio signal as shown in FIG. 3C from the demodulation circuit (6) based on the sample and hold signal shown in FIG. A predetermined portion is held and an output signal as shown in FIG. 3E is supplied to the output terminal (11).

The sample-and-hold signal generating circuit (10) generates a sample-and-hold signal as shown in FIG. 3 based on the switching signal shown in FIG. 3B supplied from the switching signal input terminal (4). ).

As shown in FIG. 3C, the above-described semiconductor integrated circuit device generates a sample and hold signal in order to reduce the noise generated when switching the reproduced multiplexed signals from the magnetic heads (la) and (1b). In circuit (10), the third
A sample-and-hold signal having a pulse width of T z (for example, 10 u s) as shown in the figure was supplied to a sample-and-hold circuit (7) to obtain an audio signal as shown in FIG. 3E.

[Problem to be solved by the invention]

Incidentally, the pulse width of the above-mentioned sample-and-hold signal, that is, the time T2, is set long in advance in consideration of the fact that the delay time of the bandpass filter (5) differs depending on the difference in its passband.

Therefore, as shown in FIG.
2 includes not only the time T3 with noise as shown in FIG. 3C, but also the time T3 without noise, that is, the delay time of this bandpass filter (5), as shown in FIG. 3C. Therefore, the sample and hold is unnecessary for the noise-free time T, and as shown in Figure 3, the sample and hold time T2 becomes longer, so when this is played back, it becomes noise. . In addition, since it is a semiconductor integrated circuit device, a sample and hold signal generation circuit (
10) It is difficult to delay the sample-and-hold signal output from.

The present invention has been made in view of the above points, and has a simple configuration, eliminates the need for adjustment, reduces noise generated when switching the reproduction signal with a minimum halt time, and outputs a highly accurate signal. This is what I did.

[Means to solve the problem]

The present invention provides a band-pass filter (5) to which an output signal from a changeover switch (3) is supplied, and an output signal from this band-pass filter (5), as shown for example in the first ward = rod≠=ll. A demodulation circuit (6) that demodulates the signal, a sample hold circuit (7) that holds a predetermined portion of the demodulated output signal from the demodulation circuit (6), and a switching signal that switches the selector switch (3) to generate a predetermined signal. In a semiconductor integrated circuit device having a sample-and-hold signal generation circuit (10) that supplies a sample-and-hold signal to a sample-and-hold circuit (7), the switching signal is
A delay circuit (9) is provided which delays based on the delay time of the bandpass filter.

[Function] According to the present invention described above, the switching signal is delayed by the delay circuit (9) based on the delay time of the bandpass filter (5), thereby achieving a simple configuration and eliminating the need for adjustment. It is possible to reduce the noise generated when switching reciprocating signals with the minimum hold time, and output highly accurate signals.

〔Example〕

An embodiment of the semiconductor integrated circuit device of the present invention will be described in detail below with reference to FIG.

In FIG. 1, two magnetic heads (1a) and (I
b) is a recording signal that is alternately recorded on the recording surface of a magnetic tape so as to form an inclined track in the longitudinal direction of the tape, that is, a pilot signal, a video signal, and an audio signal are multiplexed and recorded. The signals are alternately reproduced as shown in FIG. 3A.

These magnetic heads (1a) and (1b) each play back A
and B are supplied to the switch (3) through amplifiers (2a) and (2b), respectively.

This switch (3) alternately switches the A and B multiplexed signals based on the switching signal supplied from the input terminal (4) and sends them to the bandpass filter (5) and the video signal processing system, respectively. supply

This bandpass filter (5) has a passband of, for example, 1.5MHz, and includes a demodulation circuit (5) that extracts an audio signal as shown in FIG. 3C from the supplied multiplexed signal and performs FM demodulation.
6) to the sample and hold circuit (7).

On the other hand, the switching signal from the input terminal (4) is supplied to the delay circuit (9). This delay circuit (9) changes the delay time depending on, for example, the frequency of the clock signal from the control signal input terminal (8), and in this case, the delay time is l'B7T as shown in FIG. 3F. By changing this delay time, for example, a mode when a bandpass filter with a band of 1.5 MHz is built into the IC, a mode when a bandpass filter with a band of 1.5 MHz is installed as an external device outside the IC, etc. , a mode in which a bandpass filter with a band of 1.7 MHz is provided externally outside the IC, and other modes can be switched and set. and,
The switching signal supplied from the input terminal (4) is
As shown in FIG. F, the signal is delayed by T1 and supplied to the sample and hold signal generation circuit (10). Based on the switching signal as shown in FIG. 3F supplied from the delay circuit (9), the sample-and-hold signal generating circuit (10) generates a pulse with the same pulse width as the noisy period T3 as shown in FIG. 3G. The sample and hold signal is sent to the sample and hold circuit (7
). This allows the sample and hold circuit (
7), as shown in FIG. 3H, a predetermined portion of the audio signal is held to a minimum in accordance with the noise period T3, and a highly accurate signal with reduced noise is output.

As is clear from the above, the delay time of the delay circuit can be easily changed according to the delay time of the bandpass filter used, so the bandpass filter can be built into the IC or externally mounted outside the IC and the bandpass filter can be changed easily. The semiconductor integrated circuit device can be applied to various cases such as the above band, and the cost of the semiconductor integrated circuit device can be reduced.

[Effects of the Invention] According to the present invention described above, the delay time of the delay circuit is arbitrarily switched according to the delay time of the bandpass filter used, so the configuration is simple and adjustment is unnecessary. The noise generated when switching the playback signal is reduced with the minimum hold time, and a highly accurate signal can be output.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional example, and FIG. 3 is a timing diagram. (3) is a selector switch, (4) and (8) are input terminals,
(5) is a band pass filter, (6) is a demodulation circuit, (7
) is a sample hold circuit, (9) is a delay circuit, (10
) is a sample and hold signal generation circuit. Agent Hidemori Matsukuma Figure 3

Claims (1)

[Claims] A bandpass filter to which an output signal from a changeover switch is supplied; a demodulation circuit that demodulates the output signal from the bandpass filter; and a predetermined portion of the demodulated output signal from the demodulation circuit. A semiconductor integrated circuit device comprising a sample and hold circuit and a sample and hold signal generation circuit that supplies a predetermined sample and hold signal to the sample and hold circuit based on a switching signal that switches the changeover switch, A semiconductor integrated circuit device comprising a delay circuit that delays based on the delay time of a bandpass filter.