JPH01285052A - Control signal regenerating and writing device - Google Patents

Abstract

PURPOSE:To realize the subject device in the technology of bipolar integrated circuit by providing a switching means for selecting either an output of a regenerative amplifier or an output from a bias means. CONSTITUTION:The output of the regenerative amplifier 13 is supplied to a terminal A of a switch SW2 and a terminal A of a switch SW4. Then, in case of the regenerative state of a control signal, the switch SW2 is switched over to the side of the terminal A to select the output of the regenerative amplifier 13, and in case of the write state of the control signal, it is switched to the side of a terminal B to select the output of a bias power source 12. Moreover, an output of the switch SW2 is fed back to a negative feedback input part of the regenerative amplifier 13 via a feed back circuit consisting of resistors R1-R3, a capacitor C and the switch SW3. By this method, the degree of tolerance on a potential difference of the switch changeover for switching between the regenerative state and the recording state is alleviated, thus realizing the device sufficiently by the technology of bipolar integrated circuit.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a circuit for writing tape position information (address) using a control signal in a video tape recorder (hereinafter referred to as VTR). In particular, the present invention relates to a control signal reproducing/writing device capable of stably reproducing previously recorded control signals and stably rewriting the trailing edge of the control signal.

(Prior Art) In a home VTR, a control signal for tracking control is recorded on a dedicated control track of a tape so that the recorded track can be faithfully traced during playback.

Only the positive edge (leading edge) of the control signal is used to determine the tracking phase, and the negative edge (trailing edge)
is not used. Therefore, by changing the interval from the positive edge to the negative edge according to the "01."1" data, it is used as cue information (tape address), for example.

FIG. 3 is an example in which data "0" and "1" are represented by changing the position of the negative edge of the control signal. In other words, if the pulse width from positive edge P1 to negative edge P2 within one period T of the control signal is 60±5%, “
0", 27.5±2.5% is set as "1". If the control signal is pulse width modulated and recorded in time series based on the address data according to this rule, the control signal can be You can obtain address information by playing it.

By the way, when a recorded program is edited or modified on a recorded tape, it may be necessary to rewrite the contents of the address information. In this case, while reproducing the recorded control signal, the negative edge position must be varied again in accordance with the address data. In a VTR, reproducing cue information and address information by reproducing a previously recorded tape is an important technique because it can significantly improve editing and operability.

FIG. 4 shows an example of a conventional control signal reproducing/writing device, and FIG. 5 is a timing chart of the device shown in FIG. In FIG. 4, 1 is a control head, one terminal of which is connected to one input terminal A of switch S2 via a resistor RO, and the other terminal connected to bias power supply 2 and the other terminal of switch S2. is connected to terminal B of the The output terminal of the switch S2 is connected to the signal input terminal of the regenerative amplifier 3. Also switch S2
A write control signal R-CTL is supplied to one terminal A of the write control signal R-CTL via a switch S1. Regenerative amplifier 3
The output terminal of is connected to the waveform shaping circuit 4 and also to the negative feedback input section of the regenerative amplifier 3 via the feedback circuit R2. Further, a time constant circuit including a coupling capacitor C and a resistor R is connected between the negative feedback input section of the regenerative amplifier 3 and the bias power supply 2.

In the above configuration, the resistors R1 and R2 are connected to the regenerative amplifier 3.
The degree of amplification is determined. Further, the switch S1 is turned on when rewriting the trailing edge position of the control signal, and causes a recording current to flow to the control head 1. At this time,
The switch S2 selects the terminal B side, and the regenerative amplifier 3
A constant bias voltage is applied to the signal input terminal of.

FIG. 5 is an operation timing chart of the above circuit.

FIG. 5(a) shows a write control signal, which is supplied to the input terminal 10 of the switch S1. The positive edge of this write control signal is in phase synchronization with the reproduction control signal (obtained at the output terminal 11) (d), and the negative edge is used for cueing information or address information such as "O" or "1". The phase position is modulated based on the data. Of the control signals recorded on the tape, the portion to be rewritten is the falling phase of the negative edge, which is the trailing edge. Therefore, the switch S1 is turned off for a certain period before and after the leading edge of the control signal, and is turned on after a certain period from the leading edge. The period during which the switch S1 is off is the period during which the leading edge of the control signal is regenerated, so during this period the switch S2 selects the terminal A side, and during other periods it selects the terminal B side, that is, the bias voltage. select.

Switch 81. Control of S2 is performed by a control signal rewriting control circuit. Through such control, the recording current waveform (b
) as shown in FIG. 5(b). Also, Figure 5(c)
is the output of the regenerative amplifier 3, and (d) in the figure is the regenerative control signal obtained from the waveform shaping circuit 4. Here, the waveform shaping circuit 4 is configured such that its output rises when triggered by a pulse from the regenerative amplifier 3, and is forcibly inverted after a certain period of time.

Through the above series of operations, it is possible to write the trailing edge as a new timing while reproducing the leading edge of the control signal recorded on the tape.

In the above circuit, during the control signal rewriting period t2 to t3, the reproduction system is in a no-signal state (switch S
2 to the terminal B side to apply a bias) is that when the recording signal is amplified by the reproduction system, the potential difference between both ends of the coupling capacitor C will be different between the reproduction state and the recording state. This is to prevent drastic changes.

If this preventive measure were not taken, the potential difference of the coupling capacitor C would become a voltage different from that during playback due to the recording signal, and when the switch S1 is turned off and the mode shifts to the playback state, the voltage would return to the voltage during playback. This takes too much time and normal regeneration of the correct edge becomes impossible. The recovery time is determined by C・(R1+R2) and the potential difference, and for boat fishing, the time constant is, for example, C-47μF, R2-IMΩ,
The potential difference is so large as to be approximately 47 seconds that even a small amount of the potential difference cannot be tolerated.

(Problems to be Solved by the Invention) In recent years, various circuits have been integrated into ICs due to advances in integrated circuit technology. However, when attempting to incorporate the conventional control signal reproducing/writing device into an IC, the following problems arise. That is, the switch S2 must be a so-called analog switch, and its switching potential difference must be zero. for example,
Even if there is a switching potential difference of ll1lV, the amplification degree of the regenerative amplifier 3 is nearly 1000 times, so the output section
This occurs as an offset of v, and the large time constant makes it impossible to reproduce the positive edge. Switching potential difference is 1m
The requirement of less than V is not possible with bipolar type integrated circuit technology, and FET type integrated circuit technology must be introduced. On the other hand, as a low frequency high gain amplifier, a bipolar type is desired from the viewpoint of noise performance and high gain performance. Therefore,
In order to satisfy both performances, a manufacturing process that can realize bipolar and MOS on one chip is required.

However, this manufacturing process is expensive and
It is disadvantageous in terms of price.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control signal reproducing/writing device that is capable of reproducing and writing control signals and has a configuration that can be realized using bipolar integrated circuit technology.

[Structure of the Invention] (Means for Solving the Problems) The present invention supplies a write control signal to one terminal of a control head in a write state, and derives a reproduction control signal in a playback state, A constant bias is applied from bias means to the other terminal of the control head, and the one terminal of the control head is connected to a signal input terminal of a regenerative amplifier.

Then, either the output of the regenerative amplifier or the output from the bias means can be selected, and when reproducing the leading edge of the reproducing control signal, the output of the regenerative amplifier is selected, and after the writing control signal, the output of the regenerative amplifier is selected. Providing a switch means for selecting the output of the bias means during edge writing,
The output of this switch means is fed back to the negative feedback input section of the regenerative amplifier by a feedback circuit.

(Function) With the above means, the reference potential difference at the output section of the regenerative amplifier can be made almost zero between the writing state and the reproducing state. This is because the switch that switches between the recording state and the playback state is located at the output section of the reproducing amplifier, rather than at the signal input section, compared to conventional methods. Not amplified. Therefore, the switch can be realized with a bipolar integrated circuit without having the same effect as in the conventional case. Furthermore, since a means is provided to switch the time constant of the feedback circuit immediately after switching to the regenerative state, the regenerative amplifier can quickly return to a stable state.
A reproduction control signal can be reliably derived.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. A resistor RO that determines the reproduction and recording current is connected to one terminal of the control head 11. Also to control rad 1
A reference bias is applied to the other terminal of the transistor 1 from a bias power supply 12 .

When a recording current is supplied to the control head 11, a recording control signal R-REC is supplied from the terminal 30 via the switch SW1 and the resistor RO. Also,
When obtaining a reproduction output from the control head 11, the switch SW1 is turned off and the signal led out to one end of the resistor RO is supplied to the signal input section of the reproduction amplifier 13.

The output of the regenerative amplifier 13 is supplied to the terminal A of the switch SW2 and the terminal A of the switch SW4.

When the control signal is being regenerated, the switch SW2 is switched to the terminal A side and selects the output of the regenerative amplifier 13. When the control signal is being written, the switch SW2 is switched to the terminal B side and selects the output of the bias power supply 12. select. The output of the switch SW2 is sent to the regenerative amplifier 1 via a feedback circuit consisting of resistors R1 to R3, a capacitor C, and a switch SW3.
It is fed back to the negative feedback input section of No. 3. The switch SW3 is turned on for a predetermined period immediately after switching from the recording state to the reproducing state, as will be described later, to shorten the time constant of the feedback circuit and speed up the start-up, or recovery, of the regenerative amplifier 13. be. The gain of the regenerative amplifier 13 can be set by selecting the values of the feedback resistors R1 to R3. In addition, a bias power supply 12 and a regenerative amplifier 1 are connected in series with the resistor R1.
A coupling capacitor C connected between the negative feedback input parts of No. 3 is an element that sets the time constant of the feedback circuit.

In the reproducing state, the switch SW4 selects the terminal A side to derive the output of the regenerative amplifier 13, and selects the terminal B side to derive the bias voltage. The signal derived from switch SW4 is input to waveform shaping circuit 14. The waveform shaping circuit 14 outputs, to the output terminal 31, a reproduction control signal PB-CTL having a constant width to be used when a positive edge (leading edge) of the control signal is reproduced from the reproduction amplifier 13.

This embodiment is constructed as described above, and its operation will be described below with reference to the timing chart of FIG.

FIG. 2(a) shows the control signal R- to be recorded.
CTL and is supplied to the input terminal 30. switch S
As shown in the figure, W1 to SW2 are controlled to be on/off in a predetermined phase relationship using the positive edge (leading edge) of the reproduction control signal (e) as a reference phase. Although not shown, this switch control is performed by a timing circuit that operates during the control signal reproduction and write processing modes.

First, assuming that the switch SWI is off, the switch SW2 is connected to the terminal A side, the switch SW3 is off, and the switch SW4 is connected to the terminal A side (playback state), the playback control signal from the control head 11 is connected to its positive edge ( leading edge) is applied to the output side of the regenerative amplifier 13 (R1/R
2) and is amplified and output (FIG. 2(d)). This output (d) is sent to the waveform shaping circuit 14 via switch SW4.
The waveform is shaped by the playback control signal PB-C.
It is output as TL (Fig. 2(e)). After the positive edge is reproduced, the switch SW2 is switched to the terminal B side at time t1. As a result, both ends of the capacitor C are fixed at the same potential (bias potential), and switch SW4
The waveform shaping circuit 14 is also switched to the terminal B side.
The input terminal of is fixed to a bias voltage.

Next, at time t2, the switch SW1 is turned on and the recording current is supplied to the control head 11. This starts writing the negative edge (trailing edge). The phase position of the trailing edge is determined by the recording control signal R given from the terminal 30.
-CTL is pulse width modulated in advance according to the data content, so it is determined by the waveform of this recording control signal R-CTL (FIG. 2(b)). One time t3 after writing the negative edge, the switch SW1 is turned off, and the supply of the recording current shown in FIG. 2(c) is stopped.

After this, at one time point t4, the switch SW2 is switched to the terminal A side, and the state shifts to the normal edge reproduction state.

In this case, the time constant of the feedback circuit is switched during a certain period of time from time t4 to time t5. That is, the switch SW3 is turned on, and the time constant is changed to a small value approximately determined by the resistor R3 and the capacitor C. This is the output of the regenerative amplifier 13 (second
This is to speed up the rise in Figure (C)) and instantaneously obtain a stable state.

At time t5, the switch SW3 is turned off, the regenerative amplifier 13 has the normal gain (R1/R2), and the switch SW4 is also switched to the terminal A side, and the next reproducing control signal starts reproducing the positive edge.

By repeating the above series of operations, it is possible to reproduce the positive edges of the recorded control signal and rewrite only the negative edges.

Here, during the rewrite period (t2 to t3), both ends of the capacitor C are connected to the bias potential by the switch SW2, so there is no change in potential. And switch SW2
Since the switching is performed on the output side of the regenerative amplifier 13, even if a switching potential difference occurs, this potential difference is not amplified as in the conventional case. Furthermore, during the rewrite period (t2 to t3), the time constant is very large (it can be made large because switch SW3 is provided)
Therefore, the potential across capacitor C hardly changes.

On the other hand, during the period (tl to t4), the regenerative amplifier 13 operates as a comparator because no feedback loop is formed, and its output is fixed at either a low level or a high level. From this state, when switch SW2 is set to terminal A side at time t4 to form a feedback loop,
The operational amplifier 13 attempts to quickly return to the normal regeneration state.

However, since the output is fixed at a low level or high level, the electric charge of the instantaneous capacitor C is discharged or charged, and the transient response to cancel this charged electric charge is a series of capacitor C and resistor R2. If this happens, it will take time to stabilize. Therefore, by switching the switch SW2 from terminal B to terminal A and turning on the switch SW3 at the same time, the time constant is reduced and a stable and high-speed transition to a reproduction state is realized. In addition, the switch SW4 selects the terminal B side and derives a fixed bias voltage until the output of the regenerative amplifier 13 becomes stable through the above operation, so that only the regenerative positive edge becomes stable when inputting to the waveform shaping circuit 14. will be supplied.

In this invention, basically, the switch SW2 may be a switch that only opens the output of the regenerative amplifier 13. Furthermore, if the time required to return to the playback state can be extended, it is not necessary to provide the switch SW3.

[Effects of the Invention] As described above, according to the present invention, the tolerance to the switching potential difference of the switch that changes between the reproduction state and the recording state is relaxed, and it can be fully realized using bipolar integrated circuit technology.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a timing chart shown to explain the circuit operation of Fig. 1, and Fig. 3 shows the meaning of the phase position of the negative edge of the control signal. Waveform diagrams for explanation; Figure 4 is a diagram showing a conventional control signal reproducing/writing circuit; Figure 5 is a diagram showing a conventional control signal reproducing/writing circuit;
3 is a timing chart shown for explaining the operation of the circuit shown in the figure. 11... Control head, RO~R3... Resistor, 12... Bias power supply, 13... Regenerative amplifier, 1
4... Waveform shaping circuit, SW1 to SW4... Switch. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] A control signal reproducing and writing device for a video tape recorder includes a control head to which a write control signal is supplied to one terminal in a write state and a playback control signal is derived in a playback state; bias means for biasing the other terminal of the control head; a regenerative amplifier in which the one terminal of the control head is connected to a signal input terminal; and either the output of the regenerative amplifier or the output from the bias means. switch means for selecting the output of the regenerative amplifier when reproducing the leading edge of the reproducing control signal and selecting the output of the biasing means when writing the trailing edge of the write control signal; A control signal reproducing/writing device comprising a feedback circuit that feeds back the output of the switch means to a negative feedback input section of the regenerative amplifier.