TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 14

• Manufacturer Part Number: TEA2029
• Description: APPLICATION NOTE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

TEA2028 - TEA2029 APPLICATION NOTE
Figure 24
E - CHARACTERISTICS OF THE NON-LINEAR
AMPLIFIER ”A4” (see Figures 25 and 26)
This is a differential amplifier whose equivalent
feed-back resistors of emitters vary as a function of
its input voltage.
The maximum output voltage swing is set by two
”clamp” diodes connected to ”V
F - VOLTAGE-FREQUENCY TRANSFER
CHARACTERISTICS OF V
The transfer characteristic is linear and centered at
5.6V at 500kHz operating frequency.
T
five divide-by-two stages : T =
Figure 25 : V
-100
-150
14/46
200
160
120
100
80
40
-50
transfer
V
50
-200
0
OUT
0
V (mV)
C
/ V
=
-150
IN
V
f
5
(Degrees)
= 22.4kH/Vz and once it goes through
C
A
= F(V
-100
5.5
A = 25mV/V
22
)
-50
6
CO
22.4
(see Figure 27)
A = 50mV/V
22
32
0
” input.
6.5
20 log
= 0.7kHz/V
A
50
V
V
V
A =
300mV/V
V
C
7
IN
1 8
22
(mV)
100
(dB)
(V)
40
30
20
Figure 26 : I
0.7
0.6
0.5
0.4
Figure 27
V. 3.4. - ” 1” Time constant switching
When switching between stations or receiving sig-
nal via a VCR, the loop locking interval must be as
short as possible so as to avoid unwanted visible
effect on the picture. In fact, since the synchroniza-
tion between the VCR motor drive and the play-
back head is rather imperfect, it will produce
frequency and phase fluctuations in the output
composite video signal. Under these conditions,
phase locking interval must be ”short” (VCR Mode).
In the case of broadcast transmission, this loop
must also filter all phase variations produced by
noisy sync signal. In this case, its locking time
constant must be ”long” (normal mode).
In other ”jungle” circuits, this time constant switch-
ing is carried out by capacitor switching within the
filter loop. In our case, this function is achieved by
changing the current amplitude of the phase com-
parator.
I
22
520
500
480
( A)
= 820k
4
dV
di
2 2
5
22
22
Pin 22 VOLTAGE ” V
= F(V
dV
di
5
2 2
2 2
22
)
= 500k
5.6
518kHz
6
6
T = 22.4kHz/V
22
” (V)
dV
di
2 2
6.5
2 2
V
= 33M
2 2
7
(V)