STV5111 Просмотр технического описания (PDF) - STMicroelectronics
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STV5111 Datasheet PDF : 7 Pages
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TYPICAL APPLICATION
The STV5111 is composed of three independent
amplifiers, each of them including :
– A differential amplifier, the gain of which is fixed
by external feedback resistors,
– A voltage reference,
– A PMOS transistor providing a copy of the cath-
ode current,
– A protection diode against CRT arc discharges.
PC Board Layout
The best performances of the high voltage video
amplifier will be obtained only with a carefully desi-
gned PC board. Output to input capacitance is of
particular importance.
For a single amplifier, the input-output capaci-
tance, in parallel with the relatively high feedback
resis-tance, creates a pole in the closed-loop
transfer function.
A low parasitic capacitance (0.3pF) feedback re-
sistor and HF isolated printed wires are necessary.
Figure 3. Application Example
STV5111
Furthermore, capacitive coupling from the output
of an amplifier toward the input of another one may
induce excessive cross-talk.
Power Dissipation
The power dissipation consists of a static part and
a dynamic part. The static dissipation is a function
of VOUT(DC), VDD and RF. Reasonable approxi-
mation of the static power can be calculated by the
following equation:
Ps = 3----V----D---D----(--V--4--D-0--D--K--–-----V----O---U---T---)- + -3---V----O----U---T--(---V--R--D---FD----–-----V----O---U---T---)
The dynamic dissipation depends on the signal
spectrum, VOUT, VDD and the load capacitance.
For a sine wave, dynamic dissipation is
Pd = 3 x F x CL x VOPP x 0.8 x VDD.
The load capacitance CL includes CRT and board
capacitance (10pF), and amplifier output capaci-
tance (8pF) : total CL value is about 20pF.
VCC 9V
100m F
100nF
100nF
2
8
5
9
VDD
VDD 200V
10m F
1.2kW
1.8kW
4
VREF
7
6
12
VDD
1kW
4.7kW
CATHODE 1
10
3
11
15
VDD
CATHODE 2
13
1
14
STV5111
CATHODE 3
CUT-OFF
SAMPLING
5/7
1
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