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TA7678 LINEAR INTEGRATED CIRCUIT
VIDEO AND SOUND IF AMPLIFIER
FOR MONOCHROME TV
RECEIVERS
DESCRIPTION
The Contek TA7678 is a monolithic integrated circuit designed
for the VIF and SIF stage in B/W television receivers. The
UTC TA7678 is used for forward AGC Type.
FEATURE
VIF STAGE
*High gain wide brand IF amplifier 50dB at 45MHz
*Gain reduction with excellent stability: 55dB at 45MHz DIP-16
*Excellent DG/DP and S/N characteristics
SIF STAGE
*Excellent limiter characteristics
*Excellent AM Rejection
*Large undistorted audio output voltage with quadrature
detector
BLOCK DIAGRAM
Contek
Contek Microelectronics Co.,Ltd. 1
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CONTEK
TA7678 LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATINGS (Ta=25 C)
PARAMETER SYMBOL VALUE UNIT
Supply Voltage Vcc 15 V
Open Loop Voltage V4 15 V
Video DC output current (note) V12 6 V
Operating Temperature Topr -20 to +65 C
Storage Temperature Tstg -55 to 155 C
Power dissipation PD 1.4 W
ELECTRICAL CHARACTERISTICS(Ta=25 C,Vcc=12V,fp=45.75MHz,unless otherwise specified)
PARAMETER TEST SYMBOL TEST CONDITIONS MIN. TYP. MAX. UNIT
CIRCUIT
Recommended Supply Voltage Vcc 10.8 12 13.2 V
Quiescent circuit current 1 Iccq S1:ON,S3:2,S5:2,S4:1 35 50 65 mA
Video DC output 1 V12 S1:OFF,S3:2,S5:2,S4:1 5.2 5.5 5.8 V
Terminal 5 voltage 1 V5 S1:ON,S3:2,S5:2,S4:1 3.5 4.4 5.3 V
Terminal 7 voltage 1 V5 S1:ON,S3:2,S5:2,S4:1 4.6 6.0 7.2 V
RF AGC Residual Output Voltage 1 V4(sat) S1:OFF,S3:2,S5:2,S4:1 0.5 V
RF AGC Leak Current 1 I4(leak) S1:OFF,S3:1,S5:2,S4:1 1 mA
Video sensitivity 2 SVI Note 1 60 150 250 mVrms
AGC Range 2 VAGC(IF) Note 2 60 64 dB
Sync Tip Level Voltage (pin12) 2 Vsync Note 3 2.3 2.5 2.7 V
(pin12)
Maximum IF Input Voltage 2 VI(MAX) Note 4 100 120 mVrms
White Noise Threshold (pin12) 2 VWTH Note 5 5.8 6.2 6.6 V
(pin12)
White Noise Clamp Level (pin12) 2 VWCL Note 5 3.7 4.1 4.5 V
(pin12)
Black Noise Threshold (pin12) 2 VBTH Note 5 1.4 1.6 1.8 V
(pin12)
Black Noise Clamp Level (pin12) 2 VBCL(pin12) Note 5 2.9 3.3 3.7 V
Video Frequency Response 3 Gv(IF) Note 6 4.5 5.5 MHz
Suppression of carrier 4 CL Note 7 40 50 dB
nd
Suppression of 2 Carrier 4 I2nd Note 8 40 50 dB
920kHz Beat level 4 I920 Note 9 33 38 dB
Differentital Gain 5 DG Note 10 7 10 dB
Differential Phase 5 DP Note 10 3.5 5 C
VIF Input Impedance 6 RIN Note 11 1.5 3.0 6.0 k
CIN 3.0 10.0 pF
Maximum Avaliable Current 1 I4(MAX) Note 12 7 mA
RF AGC delay Point Range 2 Vin(delay) Note 13 5.0 7.0 9.0 V
Video output level 2 Vo0 Note 14 2.25 2.5 2.75 V
Contek Microelectronics Co.,Ltd. 2
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CONTEK
TA7678 LINEAR INTEGRATED CIRCUIT
SIF STAGE (Ta=25 C,Vcc=12V,fo=45.75MHz,unless otherwise specified)
PARAMETER TEST SYMBOL TEST CONDITIONS MIN. TYP. MAX. UNIT
CIRCUIT
SIF Output Voltage 3 VSO Note 15 200 400 600 mVrms
Input limiting voltage 8 Vi(lim) Note 16 200 400 mVrms
AM Rejection Ratio 8 AMR Note 17 40 45 dB
Recovered Output Voltage 8 VOD Note 18 0.5 0.75 Vrms
Total Harmonic distortion 8 THD Note 18 1.0 2.0 %
Maximun Audi Output Voltage 8 VOM Noet 19 4.0 Vp-p
SIF Input Impedance 7 RIN(SIF) 10 20 30 kW
CIN(SIF) 3 10 pF
Audio Output Impedance 9 RO(AF) Note 20 10 15 20 kW
Note:
1. VAGC=11.5V,VIF Input : 45.5MHz,1kHz,30 AM Modulation. Adjust VIF input Vi level so that the detected output of
Pin 12 with high impedance probe will be 0.8Vp-p and measure the input Level.
2. VAGC=4V. Measure VIF input level vi is same as note 1 DA=20log(Vi /Vi)(dB)
3. VIF input : f=45.75MHz CW 15mVrms. Measure the DC level of Pin12.
4. VIF Input : f=45.75MHz APL 100%.87.5% AM Modulation. Pin 14 Open
4.1. Adjust VIF inpt level 50mVp-p and measure the detected output level Vo(p-p)
4.2. Then increase the input level so that the detected output level will be 1.1* Vo(p-p) and measure the input
level.
5. VAGC=8V. VIF input : f=45.75MHz+-10MHz variable or sweep 15mVrms measure DC level of Pin12.
6. VAGC=8V. SG1:45.75MHz CW. SG2:45.65~27MHz variable.
6.1. Setting output of SG1 s o that the DC level of Pin12 will be
6.2. Setting output of SG1(45.65MHz so that the AC level of Pin12 will be 0.5Vp-p.
6.3. Decreasing frequency of SG2 until the AC level of Pin 12 will be 0.35vp-p(-3dB of 0.5Vp-p) then read
FSG2=F, fBW=45.75-F MHZ
7. SG1:45.75MHz, 1kHz 80% AM Modulation 100mVrms. SG2 ,SG3:OFF. Setting VAGC so that the output AC
level of Pin12 will be 2.7Vp-p. Measure CL of Pin12 after setting to 0% AM of SG1.
nd
8. Measure 2 of Pin12 same as note 9.
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CONTEK
TA7678 LINEAR INTEGRATED CIRCUIT
9. VAGC=8V. SG1 :45.75MHz(P:picture) 100mVrms, SG2:41.25MHz(S: Sound) 32mVrms(-10dB of
SG1),SG3:42.17MHz(C:Chroma) 32mVrms(-10dB of SG1)
9.1. Setting VAGC so that the output Pin12 will be 3.0V DC.
9.2. Measure the level difference between the C-level and 920kHz.
10. VAGC=8V. VIF Input : f=45.75MHz video signal (RAMP) 87.5% AM 100mVp-p. Setting ATT so that the SYNC TIP
level of Pin12 will be 2.5VDC measure DP and DG.
11. VAGC=5V. f=45.75MHz. Measure RIN and CIN.
12. S1=ON, S3=2,S5=1,S4=2
13. Pin 14 open. VIF Input : 45.75MHz CW 20mVrms.
13.1. Adjust the voltate of Pin 3 so that the voltage of Pin4 will be 6.0V DC.
13.2. Measure the Pin 3.
14. Pin 14 open. VIF Input: 45 .75MHz 100% APL 87.5% AM Modulation signal amplitude 50mVp-p mesure the
detected output voltage (white peak to SYNC TIP)
15. PIN14: Op en. SG1 :45.75MHz CW 100mvrms. SG2 :41.25MHz CW 25mVrms. Measre SIF(4.5MHz) output
voltage at Pin12.
16. SIF input: f=4.5MHz FM fMOD=400Hzm Df=+-25kHz
16.1. Adjust SIF input level 100mVp-p and measure the detected output level Vos.
16.2. Then decrease the i nput level so that the detected output level will be 3dB down of Vos and measure the
input level.
17. SIF input: f=4.5MHz, FM fMOD=400Hz Df=+-25kHz. AM 30%,input level Vins=80dB m.
18. SIF input: f=4.5MHz, fM fMOD=400Hz Df=+-25kHz. Input level Vins=80dB m
19. SIF input: f=4.4~4.6MHz variable or sweep measure the outjput DC voltage change.
20. SIF inptut : f=4.5MHz, FM FMOD=400Hz Df=+-25kHz, input level Vins=80dB m.
20.1. Measure the detected output voltagae vOA with Rx= .
20.2. Then, adjust Rx so that the d etected output voltage will be VOA/2 and measure Rx.
1. DC TEST CIRCUIT
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CONTEK
TA7678 LINEAR INTEGRATED CIRCUIT
2. AC TESTS CIRCUIT
3. VIDEO FREQUENCY RESPONSE & SIF OUTPUT VOLTAGE TEST CIRCUIT
4. INTER MODULATION TEST CIRCUIT
Contek Microelectronics Co.,Ltd. 5
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CONTEK
TA7678 LINEAR INTEGRATED CIRCUIT
5. DG,DP TEST CIRCUIT
5. INPUT IMPEDANCE TEST CIRCUIT
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CONTEK
TA7678 LINEAR INTEGRATED CIRCUIT
7. SIF INPUT IMPEDANCE TEST CIRCUIT
8. VIN(LIM) AMR, VOD,THD VOM TEST CIRCUIT
9. AUDIO OUTPUT IMPEDANCE TEST CIRCUIT
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TA7678 LINEAR INTEGRATED CIRCUIT
TYPICAL APPLICATION CIRCUIT
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CONTEK