Digital magnetic recording/reproducing amplifying apparatus

A digital magnetic recording/reproducing amplifying apparatus which includes a recording amplifying portion, a first reproducing amplifying portion, a switching portion, and a second reproducing amplifying portion. The apparatus has the advantage of uniform performance by a more simply defined recording current waveform with variable resistance and by performing a two-stage amplification while simultaneously reducing the number of amplifiers by half.

FIELD OF THE INVENTION 
The present invention relates to a data recording/reproducing amplifying 
apparatus for digital video tape recorders (VTRs), and more particularly 
to a data recording/reproducing amplifying apparatus for recording and 
reproducing large quantities of data. 
BACKGROUND OF THE INVENTION 
A conventional digital VTR system is shown in FIG. 1 in which analog video 
signals inputted via input terminal IN(1) are converted to digital signals 
in an analog/digital converter 10 of an input portion A and are 
transmitted to a synchronizer 40 through a first error corrector 20 and a 
modulator 30. During this operation, a clock generator 60 generates clock 
signals from a reference signal inputted via input terminal IN(3) and 
transmits the clock signals to the first error corrector 20, modulator 30, 
and a synchronizer 40. The synchronizer 40 adds the clock signals 
generated from the clock generator 60 to signals received from the 
modulator 30. The resultant signal is supplied to head 80 through a 
recording equalizer 50 and a recording amplifier 70. A head 80 converts 
the signals amplified in the recording amplifier 70 into a current 
waveform and records it on tape 90. 
In order to reproduce the signals recorded on the tape 90, the signals are 
changed to electric signals by the head 80, then are amplified by a 
reproducing amplifier 100. After that, the signals pass through a 
reproducing equalizer 110, a pulse detector 120, a synchronizing detector 
130, a demodulator 140, a TBC (Time Base Corrector) 150, and a second 
error corrector 170 all of which constitute an output portion, and then 
the signals are converted into analog signals by a digital/analog 
converter 180. During this operation, a clock reproducer 160 receives 
output signals from the reproducing equalizer 110 and reproduces clock 
signals which are then applied to the pulse detector 120, synchronizing 
detector 130, demodulator 140 and TBC 150. Input terminal IN2 and output 
terminal OUT2 are used when digital video signals are directly inputted or 
outputted. 
Conventional digital VTR systems, however, have a problem in that the 
recording amplifier 70 and reproducing amplifier 100 have overly 
complicated circuitry to precisely record digital signals on the tape 90. 
OBJECT OF THE INVENTION 
Therefore, it is an object of the present invention to provide a data 
recording and reproducing/amplifying apparatus having simpler circuitry 
than a conventional one yet maintaining performance characteristics of a 
conventional one. 
SUMMARY OF THE INVENTION 
To accomplish these and other objects, a digital VTR system is provided 
which includes an input portion which receives analog video signals and 
converts them to digital video signals, an output portion which converts 
the digital video signals to analog video signals, a clock signal 
generator which supplies clock signals to the input and output portions 
according to the reference input, and a clock reproducer provided in the 
output portion. Preferred embodiments of the invention also include: a 
recording amplifying portion for converting digital signals outputted from 
the recording equalizer into current signals; a first reproducing 
amplifying portion which amplifies and outputs current signals recorded on 
a tape and detected by a plurality of heads; a switching portion which 
switches signals received from the first reproducing amplifying portion; 
and a second reproducing amplifying portion which again amplifies the 
output signals from the first reproducing amplifier, through selected 
switches in the switching portion and then supplies the resultant signals 
to the reproducing equalizer of the output portion, thereby amplifying the 
signals.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 2, a recording amplifying portion 70a of an apparatus 
according to the invention includes amplifiers AMP1 and AMP2 which are 
connected to and amplifying the output of the recording equalizer 50 of 
the input portion A shown in FIG. 1. Four heads 80b, 80c, 80d, and 80e, 
are attached to a drum 80a for recording or reproducing signals on the 
tape 90 as shown in FIG. 1. The four heads are also connected to the 
output terminals of amplifiers AMP1 and AMP2 of the recording amplifying 
portion 70a, with heads 80c and 80e driven by AMP1 and heads 80b and 80d 
driven by AMP2 respectively. Within a first reproducing amplifying portion 
100a, reproducing amplifiers AMP3, AMP4, AMP5 and AMP6 are respectively 
connected to heads 80b, 80c, 80d and 80e of the drum 80a for amplifying 
detected signals. A switching portion 100b having switches SW1, SW2, SW3 
and SW4 for switching signals outputted from the reproducing amplifiers 
AMP3 and AMP4 and signals outputted from the reproducing amplifiers AMP5, 
AMP6 is connected to each reproducing amplifier's output terminal. The 
switches SW1, SW2, SW3 and SW4 of the switching portion 100b are also 
connected to a second reproducing amplifying portion 100c having 
amplifiers AMP7 and AMP8 which amplify signals selectively switched and 
supply the signals to the reproducing equalizer 100 of the output portion 
B, as shown in FIG. 1. 
The following is a more detailed description of the invention referring to 
FIGS. 2, 3 and 4. 
As shown in FIG. 2, supplying digital signals as shown in FIG. 4A, which 
are outputted from recording equalizer 50 of FIG. 1 to heads 80b, 80c, 80d 
and 80e mounted on drum 80a, recording amplifiers AMP1 and AMP2 convert 
the digital signals to the current waveform of FIG. 4B. Amplifier AMP1 
drives the heads 80b, and 80d and amplifier AMP2 drives the heads 80c, and 
80e. 
Referring to FIG. 3A, digital data transmitted from the recording equalizer 
50 is applied to transformer T1 as the waveform of FIG. 4C and is then 
converted to balanced signals. The balanced signals outputted from 
transformer T1 are supplied to the base of transistors Q1 and Q2. 
The balance signals as shown in FIG. 4D turn the above transistors on and 
off. A constant current circuit composed of transistor Q3, resistances R2, 
R3 and R4, and diode D1 maintain a constant current to a transformer T2 
through transistors Q1 and Q2. 
Transistor Q4 and resistances R5 and R6 are controlled by a recording 
control signal Rc in such a manner that amplifiers AMP1 and AMP2 only 
operate when recording and do not operate when reproducing. Combined with 
the inductance of transformer T2, variable resistance VR1, which is 
connected to collectors of the transistors Q1 and Q2, is used to shape a 
current waveform whose rise and fall time (.tau.) is determined by the 
values of the inductance L of transformer T2 and resistance R of variable 
resistance VR1. The formula is as follows: 
##EQU1## 
A current square wave outputted to output terminal OUTPUT and following the 
above formula is controlled as shown in FIG. 4G to improve transient 
response characteristics during rise time and fall time. FIG. 4E shows the 
current square wave when a transient response is excessive and FIG. 4F 
shows when a transient response arrives at its normal state in haste. 
In order to reproduce data recorded on tape 90 by the heads, 80c, 80e, 80b, 
and 80d, which are mounted on drum 80a, input terminals of reproducing 
amplifiers AMP3, AMP4, AMP5 and AMP6 are connected to heads 80b, 80c, 80d 
and 80e, respectively, to amplify the recorded signal. Then, using 
switching portion 100b, the outputs of amplifiers AMP3 and AMP4 or 
amplifiers AMP5 and AMP6 are alternately selected. 
Control signal waveforms supplied to terminals 1 and 2 of the switching 
portion 100b are shown in FIGS. 4H and 4J which control the output signals 
from the reproducing amplifiers AMP3, AMP4, AMP5 and AMP5, and which is 
transmitted to reproducing equalizer 110 via reproducing amplifiers AMP7 
and AMP8, as the waveforms shown in FIGS. 4K and 4L. The reproducing 
amplifiers AMP3, AMP4, AMP5, AMP6, AMP7 and AMP8 all have the same circuit 
structure as the reproducing amplifier shown in FIG. 3B. 
The present invention has an advantage of uniform performance during 
digital magnetic recording, by more simply shaping the recording current 
waveform with a variable resistance, and also improved performance during 
reproducing, by performing a two-stage amplification while reducing the 
number of amplifiers by half.