JPH0983257A - VTR control head amplifier device - Google Patents

Abstract

(57) Abstract: To reduce the influence of voltage fluctuation of a bias power supply on the final output of the device. A bias power source supplies a bias voltage to a differential amplifier, and both terminals of a control head of a video tape recorder are connected to a first input terminal of the differential amplifier.
The first and second input terminals 52 are respectively connected to amplify the potential difference between both ends of the control head 1. The reference input terminal 56 of the non-inverting amplifier 5 and the bias power supply 4 are connected via the capacitor 3, the output terminal 53 of the differential amplifier 2 is connected to the signal input terminal 55 of the non-inverting amplifier 5, Amplifies the output signal. The voltage fluctuation of the bias power supply 4 is input not only to the signal input terminal 55 of the non-inverting amplifier 5 but also to the reference input terminal 56 in the same phase. The removal function cancels the output fluctuation due to the voltage fluctuation of the bias power supply 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VTR control head amplifier device for amplifying a reproduction control signal obtained from a control head in a VTR (video tape recorder).

[0002]

2. Description of the Related Art In recent years, a VTR control head amplifier device has been used in which both ends of a VTR control head are directly connected to a differential amplifier, thereby eliminating the capacitor required for capacitive coupling between one end of the conventional control head and the amplifier. It's starting to happen. A conventional VTR control head amplifier device will be described below.

FIG. 3 is a schematic block diagram of a conventional VTR control head amplifier device, and 1 is a control head. Reference numeral 2 denotes a differential amplifier in which both terminals of the control head 1 are connected to a first input terminal 51 and a second input terminal 52, respectively, and a potential difference between both ends of the control head 1 is amplified and output from an output terminal 53. Reference numeral 4 is a bias power supply for supplying a bias voltage to the bias voltage input terminal 54 of the differential amplifier 2. 5, the output terminal 53 of the differential amplifier 2 is connected to the signal input terminal 55,
Of the output signal from the output terminal 53 of the
It is a non-inverting amplifier that outputs more. 3 is a non-inverting amplifier 5
Is a capacitor that is connected between the reference input terminal 56 and the ground (GND) and capacitively couples the reference input terminal 56 of the non-inverting amplifier 5 and the ground (GND).

FIG. 4 is a circuit diagram showing a specific configuration of the differential amplifier 2 and the non-inverting amplifier 5 shown in FIG. In FIG. 4, the differential amplifier 2 includes resistors 71 to 74 and an operational amplifier 7.
It is composed of 5. Further, the non-inverting amplifier is composed of resistors 76 and 7
7 and operational amplifier 78. The operation of the conventional VTR control head amplifier device configured as described above will be described below.

First, when a tape is reproduced by a VTR, a control signal is induced as an electromotive force at both ends of the control head 1 and a potential difference is generated between the first input terminal 51 and the second input terminal 52 of the differential amplifier 2. Next, the potential difference between the first input terminal 51 and the second input terminal 52 of the differential amplifier 2 is amplified by the differential amplifier 2 using the bias voltage from the bias power supply 4 as a reference voltage, and the output terminal 53 of the differential amplifier 2 is amplified.
Output. Next, the output terminal 53 of the differential amplifier 2
The output signal from is sent to the input terminal 55, further amplified by the non-inverting amplifier 5, and output from the output terminal 57 of the non-inverting amplifier 5. At this time, since the reference input terminal 56 of the non-inverting amplifier 5 is capacitively coupled to the ground GND by the capacitor 3, the reference voltage of the non-inverting amplifier 5 becomes substantially equal to the bias voltage of the bias power supply 4. As a result, the reproduction control signal induced at both ends of the control head 1 is amplified by the differential amplifier 2 and the non-inverting amplifier 5, and the final output is a signal amplified with the bias voltage of the bias power source 4 as the reference voltage.

[0006]

However, in the above-mentioned conventional configuration, the voltage fluctuation of the bias power supply 4 used for the differential amplifier 2 is directly amplified by the non-inverting amplifier 5 in the next stage. The final output is the bias power supply 4
However, there is a problem that it is greatly affected by the voltage fluctuation of

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a VTR control head amplifier device which can reduce the influence of the voltage fluctuation of the bias power supply at the final output of the device.

[0008]

According to the VTR control head amplifier device of the present invention, both terminals of a control head of a video tape recorder are connected to a first input terminal and a second input terminal, respectively, of a control head of a video tape recorder. A differential amplifier that amplifies the potential difference between both ends, a bias power supply that applies a bias voltage to the differential amplifier, and a non-inverting amplifier that amplifies the output signal of the differential amplifier by connecting the output terminal of the differential amplifier to the signal input terminal. An amplifier,
The non-inverting amplifier includes a capacitor connected between the reference input terminal and the bias power supply.

According to the configuration of the present invention, the voltage fluctuation of the bias power supply is input not only to the signal input terminal of the non-inverting amplifier but also to the reference input terminal in the same phase, thus configuring the non-inverting amplifier. The in-phase signal removing function of the operational amplifier cancels the output fluctuation due to the voltage fluctuation of the bias power supply.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of a VTR control head amplifier device according to an embodiment of the present invention. The difference between this VTR control head amplifier device and the conventional example is that
The point is that one end of the capacitor 3 is connected to the bias power source 4 instead of being connected to the ground GND. Other configurations are the same as those of the conventional example, and the description thereof will be omitted.

FIG. 2 is a circuit diagram showing a specific configuration of the differential amplifier and the non-inverting amplifier shown in FIG. 1, and the configurations of the differential amplifier and the non-inverting amplifier are the same as those of the conventional example. The operation of the VTR control head amplifier device of the embodiment configured as described above will be described below. First, V
When the tape is reproduced by TR, a control signal is induced as an electromotive force at both ends of the control head 1, and a potential difference is generated between the first input terminal 51 and the second input terminal 52 of the differential amplifier 2. Next, the first input terminal 51 of the differential amplifier 2
And the potential difference between the second input terminal 52 and the second input terminal 52 are amplified by the differential amplifier 2 using the bias voltage from the bias power supply 4 as a reference voltage and output from the output terminal 53 of the differential amplifier 2. Next, the output signal from the output terminal 53 of the differential amplifier 2 is sent to the input terminal 55, further amplified by the non-inverting amplifier 5, and output from the output terminal 57 of the non-inverting amplifier 5.
At this time, the reference input terminal 56 of the non-inverting amplifier 5
Is capacitively coupled to the bias power supply 4 by the capacitor 3, so that the reference voltage of the non-inverting amplifier 5 becomes substantially equal to the bias voltage of the bias power supply 4. As a result, the reproduction control signal induced at both ends of the control head 1 is amplified by the differential amplifier 2 and the non-inverting amplifier 5, and the final output becomes a signal amplified with the bias voltage of the bias power source 4 as the reference voltage. The same operation as the example can be performed.

Now, the reason why the same operation as the conventional example can be performed will be described. The reference input of the non-inverting amplifier 5 is capacitively coupled to the ground GND in the conventional example, and is capacitively coupled to the bias power supply 4 in the embodiment. However, because of the capacitive coupling, the ground GND or the connection destination of the capacitor 3 or The bias power source 4 does not supply the reference voltage to the non-inverting amplifier 5. The non-inverting amplifier 5 whose reference input is capacitively grounded can be seen as a voltage follower in terms of direct current, and its output is supplied by the reference voltage of the differential amplifier 2 in the preceding stage from the input. Behaves as if it were the reference voltage of the non-inverting amplifier 5. Therefore, regardless of where the reference capacitor 3 of the non-inverting amplifier 5 is connected, the same operation as the conventional example can be performed.

Further, the voltage fluctuation of the bias power source 4 is directly transmitted to the output terminal 53 of the differential amplifier 2 and input to the signal input terminal 55 of the non-inverting amplifier 5, and the voltage fluctuation of the bias power source 4 is passed through the capacitor 3. It is also input to the reference input terminal 56 of the non-inverting amplifier 5 as it is. As a result, the signal input terminal 55 of the non-inverting amplifier 5 and the reference input terminal 56 of the non-inverting amplifier 5 are almost in-phase signal inputs. The influence of the voltage fluctuation hardly appears at the output terminal 57 of the non-inverting amplifier 5.

As described above, according to this embodiment,
By connecting the capacitor 3 between the reference input terminal 56 of the non-inverting amplifier 5 and the bias power supply 4 used in the differential amplifier 2 in the preceding stage, even if the voltage of the bias power supply 4 changes, the voltage of the non-inverting amplifier 5 remains unchanged. Since the fluctuation is canceled, it is possible to prevent the output terminal 57 of the non-inverting amplifier 5 from being affected by the voltage fluctuation. Further, even if this configuration is adopted, the conventional performance as the control head amplifier does not deteriorate.

[0015]

According to the present invention, since the reference input terminal of the non-inverting amplifier and the bias power supply used for the differential amplifier in the preceding stage are connected by a capacitor, the influence of the voltage fluctuation of the bias power supply is almost eliminated. It is possible to realize an excellent VTR control head amplifier device that can be realized.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a VTR control head amplifier device according to an embodiment of the present invention.

2 is a circuit diagram showing a specific configuration of a differential amplifier and a non-inverting amplifier in the VTR control head amplifier device of FIG.

FIG. 3 is a schematic block diagram of a conventional VTR control head amplifier device.

4 is a circuit diagram showing a specific configuration of a differential amplifier and a non-inverting amplifier in the VTR control head amplifier device of FIG.

[Explanation of symbols]

 1 Control Head 2 Differential Amplifier 3 Capacitor 4 Bias Power Supply 5 Non-Inverting Amplifier 51 First Input Terminal 52 Second Input Terminal 53 Output Terminal 54 Bias Voltage Input Terminal 55 Signal Input Terminal 56 Reference Input Terminal 57 Output Terminal 71-74 Resistor 76-77 resistor 75,78 operational amplifier

Claims (1)

[Claims] 1. A differential amplifier for connecting both terminals of a control head of a video tape recorder to a first input terminal and a second input terminal, respectively, for amplifying a potential difference between both ends of the control head of the video tape recorder, and A bias power supply for applying a bias voltage to the differential amplifier,
A non-inverting amplifier having an output terminal of the differential amplifier connected to a signal input terminal for amplifying an output signal of the differential amplifier;
A VTR control head amplifier device comprising a capacitor connected between a reference input terminal of the non-inverting amplifier and the bias power supply.