JPH0244880A - Hold circuit - Google Patents

Abstract

PURPOSE:To lower the distortion rate of a reproduced sound signal by providing a second amplifier and a second SW circuit to make the reproduced sound signal take a roundabout route without passing through an integration circuit constituted of a first SW circuit and a capacitor at ordinary time, and using a signal stored in the integration circuit during a period in which a noise is to be removed. CONSTITUTION:When the reproduced sound signal is inputted to an input terminal 1, the reproduced sound signal through an amplifier 6 is outputted to an output terminal 2 by the SW circuit 9. Besides, at the time of the switching to two sound heads fitted to a cylinder head, the reproduced sound signal have been inputted to the amplifier 4 is cut off by turning the SW circuit 8 off by inputting a switching signal from a switching control input terminal 10, and the amplifier 5 is driven by potential charged in a capacitor 7, and the output of the output level of the potential same as the potential charged in the capacitor 7 is outputted to the output terminal 2. Thus, the distortion rate of the reproduced sound signal can be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hold circuit, and in particular, to a hold circuit for a VTR.
This invention relates to a hold circuit that holds the noise period that occurs when switching between two audio heads attached to a cylinder head when demodulating Fi audio.

[Conventional technology]

A conventional hold circuit will be explained using FIG. 2.

In the hold circuit shown in FIG. 2, the input of the amplifier 4 is input terminal 1, the output is connected to the amplifier 5 and one end of the capacitor 7 via the SW circuit 8, and the other end of the capacitor 7 is connected to the low potential terminal 3. The output of the amplifier 5 is set as the output terminal 2, and the SW circuit 8
The configuration was such that it had a switching control input.

VTR cr) When demodulating Hl-Fi audio, a magnetic tape is wound around the cylinder head, and the FM modulated signal of H i -Fi, which is azimuthally recorded, is extracted as a continuous signal by switching between two audio heads. However, the moment the two audio heads are switched, the Hi-Fi audio FM
Since the modulation signal is interrupted and a large noise is generated in the reproduced audio signal, the SW circuit 8 of the hold circuit is turned off by inputting a switching signal from the switching control human power 10 for the period of this noise, and the signal is input to the input terminal 1 of the bold circuit. The second amplifier 5 at the rear stage is driven by the potential charged in the capacitor 7, and the capacitor 7 is connected to the output end 2.
It was outputting an output level that was the same potential as the potential charged in it.

Also, when one of the two audio heads (the one that is in contact with the magnetic tape) is operating, the S
The W circuit 8 is turned on, and the reproduced audio signal that has entered the input of the hold circuit is outputted via the amplifiers 4 and 5.

[Problem to be solved by the invention]

In the conventional hold circuit described above, Sw times Fl @ 8 is O
During normal operation, the hold circuit has a disadvantage in that the distortion rate worsens depending on the frequency of the input reproduced audio signal (f'N≧8KHz) due to the integration circuit formed by the ONN resistor and the capacitor 7.

[Means to solve the problem]

The hold circuit of the present invention connects the first output to the third amplifier and one end of the capacitor via the first 8W circuit, and the other end of the first capacitor. is connected to the low potential terminal, and the output of the third amplifier is connected to the second
The second input of the second SW circuit is connected to the first input of the second SW circuit.
, the output of the second SW circuit is connected to the input of the first SW circuit, and the output of the second SW circuit is connected to the input of the first SW circuit. The switching control input of the second SW circuit is configured as a switching control terminal.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

The reproduced audio signal input from the input terminal 1 is transmitted to the 18th. Second
from the output of amplifier 4 to the inputs of amplifiers 4 and 6.
It enters the first input of the second SW circuit 89 via the SW circuit 8 and the third amplifier 5.

Also, the reproduced audio signal input to the amplifier 6 is input to the amplifier 6.
It enters the second input of the 8W circuit 9 from the output of the SW circuit 9.
One of the signals inputted from the first or second input of the 8W circuit 9 is outputted to the output terminal.

Also, a capacitor 7 is inserted into the low potential terminal from the connection point between the SW circuit 1i48 and the amplifier 5.

The switching timing between the SW circuit 8 and the SW circuit 9 is the first
．． When the SW circuit 8 is OFF in synchronization with the switching signal of the switching control input terminal connected to the switching control input of the second SW circuit 8, 9, the output of the SW circuit 9 is The signal input from the first input is output, and the SW circuit 8
is ON, the second output of the circuit 9 is connected to the output of the SW circuit 9.
The signal input from the input is output.

With the above configuration, when a playback audio signal is input to input terminal 1,
A reproduced audio signal via the amplifier 6 is outputted from the SW circuit 9 to the output terminal 2 .

Also, when switching between the two audio heads attached to the cylinder head, the SW circuit 8 is connected to the output terminal 2 and the switching control input terminal 10 is connected to the output terminal 2.
A switching signal is input to turn it off, cutting off the reproduced audio signal input to the amplifier 4, driving the amplifier 5 with the potential charged in the capacitor 7, and transmitting the signal charged to the capacitor 7 to the output terminal 2. The output level is the same as the potential that was applied.

〔Effect of the invention〕

As explained above, the present invention provides a second amplifier and a second amplifier that bypass the reproduced audio signal without passing it through the integrating circuit formed by the SW circuit and the capacitor except during the noise removal period, that is, during normal times. By using the signal accumulated in the integrating circuit during the noise removal period, the SW circuit has the effect of greatly improving the distortion rate of the reproduced audio signal.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 2 is a circuit diagram showing a conventional example. 1...Input end, 2...Output end, 3...
...Low potential end, 10...Switching control end, 4,5.6
...Amplifier, 7...Capacitor, 8,9.
...SW circuit. No.? Strict

Claims (1)

[Claims] The input terminals of the first and second amplifiers are the input terminals of the first and second amplifiers, and the first output is the input terminal of the first amplifier.
The third amplifier is connected to one end of the capacitor through the SW circuit, the other end of the capacitor is connected to the low potential end, and the output of the third amplifier is connected to the first input of the second SW circuit. connected to a second input of the second SW circuit;
A hold circuit characterized in that the output of the W circuit is an output terminal, and the switching control inputs of the first and second SW circuits are switching control terminals.