1
Video ICs
4-channel video-signal PRE / REC
amplifier
BA7274S
The BA7274S PRE / REC amplifier has been designed for use in video cassette recorders. It is compatible with four-
head decks, and has four head amplifiers, a chroma output amplifier, and FM output amplifier (with AGC circuit), an
envelope detector, a fixed-current drive recording amplifier, a channel switch circuit, and record / playback switch
integrated only one monolithic IC.
•Applications
VCRs
•Features
•Absolute maximum ratings (Ta = 25°C)
•Recommended operating conditions (Ta = 25°C)
Power supply voltage
Power dissipation
Operating temperature
Storage temperature
∗ Reduced by 11.0mW for each increase in Ta of 1°C over 25°C.
Parameter Symbol Limits Unit
VCC 7 (PRE) 13 (PRE) V
Pd 1370∗mW
Topr – 20 ~ + 70 °C
Tstg – 55 ~ + 150 °C
Operating power supply voltage (playback)
Operating power supply voltage (recording)
∗ The PRE and REC VCC are used for mode switching. If the PRE and REC VCC voltages are applied
together, the amplifier systems and head switch will go on simultaneously causing a large current to
flow. This must be avoided, so do not make pins 21 and 25 "H" (0.5V or more) together.
Parameter Symbol Min. Typ. Max. Unit Conditions
VCC (P)
VCC (R)
4.5 5.0 5.5 V 25pin
11.5 12 12.5 V 21pin
1) Suitable for 4-head decks.
2) Integration of the head-section signal processing cir-
cuits (REC and head amplifiers, AGC, and envelope
detector) only one IC allows compact deck designs.
3) The head amplifier has low input capacitance and
low noise (VNIN = 0.4µVrms), and both the playback
and recording systems have a wide frequency
range.
4) The REX amplifier employs a fixed-output current
system to minimize change in the recording current
due to load fluctuation. The maximum recording cur-
rent output is a large 30mAP-P.
5) Built-in channel and record / playback switches
(switched to PB VCC and REC VCC).
6) Peaking amplifier pin provided for external setting of
peak value.
7) Compact SDIP 32 pin package.
8) Auto-tracking compatible.
2
Video ICs BA7274S
•Block diagram
AGC DET
AGC AMP PEAKING
ENVE. COMP
PRE
V
CC
ENVE
DET
HSW
PRE 1 PRE 2
ENVE
DET
HSW
PRE 3 PRE 4
PRE
GND GND
REC
EQ
SW
PRE
HA
SW
EQ CTRL
H SW CTRL
–
+
HA SW CTRL
V
CC
31
32
30
29
28
27
26
25
24
23
22
21
20
19
18
17
2
1
3
4
5
6
7
8
9
10
11
12
13
14
15
16
3
Video ICs BA7274S
•Electrical characteristics (unless otherwise noted, Ta = 25°C)
〈Playback system〉 VCC = 5V
Supply current
Voltage gain (CH1 to CH4)
Maximum chroma output level
AGC output amplitude level
AGC control sensitivity
AGC freguency char. (CH1 to CH4)
Crosstalk
Input conversion noise (CH1 to CH4)
Head switching threshold voltage
Head amplifier switching threshold voltage
ENVELOPE comparison output amplitude
COMP (ENVE) switch threshold
ENVE detector output level SP
ENVE detector output level SP
ENVE detector output level EP
ENVE detector output level EP
PRE switch on resistance
〈Recording system〉 VCC = 12V
Supply current
Maximum output current
Recording current secondary distortion
Recording current load characteristics
Recording current freguency char.
EP / SP switching threshold voltage
REC switch ON resistance
Parameter Symbol Min. Typ. Max. Unit Conditions
ICC-P 23 34 44 mA
GVP 49 57 62 dB
VOMC 1.3 1.5 —
VAGC 130 180 220
– 1.0 1.0 3.0 dB
Gf1 ~ 4 – 2.0 2.0 4.0 dB
—– 40 – 33 dB
VN1 ~ 4 — 0.4 1.2 µVrms
VTH3 2.0 2.5 3.0 V
VTH4 2.0 2.5 3.0 V
V24 4.3 ——V
VTHP2 0.3 1.3 1.8 V
1.3 1.6 2.1 V
2.6 2.9 3.3 V
1.3 1.6 1.9 V
3.4 3.7 4.1 V
R16, 18 —510Ω
30 47 65 mA
IL30 ——mAP-P
DL—– 35 dB
—13mA
Gf– 5 – 3 1.5 dB
0.8 1.3 1.8 V
R5, 7, 10, 12 — 10 15 Ω
– 31
VP-P
mVP-P
VTHR 2
CT
VENV-S1
VENV-S2
VENV-E1
VENV-E2
ICC-R
∆VAGC
∆IL
—
4MHz
IL = 30mA, 4MHz, 8.2 ~ 15µH
High: EP Low: SP
VIN = 0.3mVP-P, 100kHz
VIN = 0.3mVP-P, 10MHz / 1MHz
High: CH1, 4 Low: CH2, 3
High: CH3 or 4 Low: 1 or 2
CHROMA OUT = 0.0VP-P
High: STOP Low: ENVE OUT
CHROMA OUT = 0.5VP-P, 4MHz
CHROMA OUT = 0.0VP-P
CHROMA OUT = 0.5VP-P, 4MHz
IL = 30mAP-P, 4MHz
IL = 10mA, 8MHz / 100kHz
VIN = 0.15 ~ 0.6mVP-P, 4MHz
High: CH1 or 2 > CH3 or 4
Low: CH3 or 4 > CH1 or 2
4
Video ICs BA7274S
•Measurement circuit
AGC DET
AGC AMP PEAKING
ENVE. COMP
PRE
V
CC
ENVE
DET
HSW
PRE 1 PRE 2
ENVE
DET
HSW
PRE 3 PRE 4
PRE
GND GND
REC
EQ
SW
V
CC
HA
SW
1µ
30p
1.5k
33µ
5.1k
AGC OUT
AGC OUT
OUT 0.01µ
CHROMA
OUT
ENVE
PRE
VCC
5V
COMP. OUT
0.01µ
50k
0.01µ
REC VCC
12V
0.01µ
50
200
0.0047µ
REC IN
100
0.1µ
510
0.1µ
10
0.1µ
0.1µ
0.1µ
10
10
10
1µ
0.1µ10
0.1µ10
560
1µ
560
1µ
560
0.1µ10
0.1µ10
1µ
560
EQ CTRL
HSW CTRL
510
REC
HEAD AMP SW CTRL
PRE IN ch4
PRE IN ch3
PRE IN ch2
PRE IN ch1
HEAD SW CTRL
C [F]
L [L]
REC CURRENT SENSE
EQ CTRL HA SW CTRL
Units: R [Ω]
Fig. 1
2
1
3
4
5
6
7
8
9
10
11
12
13
14
15
16
31
32
30
29
28
27
26
25
24
23
22
21
20
19
18
17
+
+
+
+
+
5
Video ICs BA7274S
•Application example
HEAD
SP A
SP B
H SW
PRE Y.OUT
PRE VCC 5V
PRE C.OUT
REC VCC 12V
REC C.IN
REC Y.IN
AGC DET
AGC AMP PEAKING
ENVE. COMP
PRE
V
CC
ENVE
DET
HSW
PRE 1 PRE 2
ENVE
DET
HSW
PRE 3 PRE 4
PRE
GND GND
REC
EQ
SW
PRE
HA
SW
EP A
EP B
EP ‘‘H’’
EQ CTRL
H AMP SW
H SW CTRL
ENVE (COMP) OUT
ENVE (DET) OUT
+
HA SW CTRL
V
CC
Fig. 2
31
32
30
29
28
27
26
25
24
23
22
21
20
19
18
17
2
1
3
4
5
6
7
8
9
10
11
12
13
14
15
16
–
6
Video ICs BA7274S
•Control pin logic
(1) Playback head switching
HEAD SW
3pin
LH
L
HL
H
H. AMP SW 14pin Selected head
CH1 (PRE AMP pin 5 input)
CH2 (PRE AMP pin 7 input)
CH3 (PRE AMP pin 10 input)
CH4 (PRE AMP pin 12 input)
(2) EP / SP switching envelope comparator ON / OFF switch (pin 2)
H
(REC) LH
L
LH
(PB)
H
L
EP (REC AMP pin 16 output)
SP (REC AMP pin 17 output)
ENVE. detector output pin 26 EP mode
ENVE. comparator output pin 24 stopped "H"
ENVE. detector output pin 26 SP mode
ENVE. comparator output pin 24 operating, see (3)
Mode
REC VCC
21pin PRE VCC
25pin 2pin
EP / SP
Conditions
CH1 or CH2 output > CH3 or CH4 output
CH1 or CH2 output < CH3 or CH4 output
24pin
H
L
COMP. OUT
(3) Envelope comparator output (pin 24)
CH CH1 CH2 CH3 CH4
PRE AMP PRE AMP 1 PRE AMP 2 PRE AMP 3 PRE AMP 4
Note: The correspondence between channels and amplifiers is as follows:
7
Video ICs BA7274S
3000 100 200 400 500 600 700 800 9001000
0
1
2
3
4
5
EP
SP
Fig. 1 Playback signal envelope
detector characteristics
ENVELOPE DETECTOR OUTPUT
VOLTAGE: (VDC)
OUTPUT VOLTAGE 28pin (mVP-P)
•Electrical characteristic curve
•External dimensions (Units: mm)
SDIP32
4.7 ± 0.3
0.51Min.
8.4 ± 0.3
3.2 ± 0.2
32
116
17
0.5 ± 0.1
0.3 ± 0.1
28.0 ± 0.3
0° ~ 15°
10.16
1.778
