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| 型號(hào)： | SA572F |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | Programmable analog compandor |
| 中文描述： | COMPANDER, CDIP16 |
| 文件頁(yè)數(shù)： | 5/8頁(yè) |
| 文件大?。?/td> | 125K |
| 代理商： | SA572F |
V
IN
V
REF
V+
A2
+
–
R2
Q6
Q5
D7
IR
VIN
VREF
R
2
Figure 2. Simplified Rectifier Schematic
Q8
Q9
Q10
Q17
X2
Q16
X2
Q18
10k
D13
Q14
CR
D15
A3
10k
D11
D12
CA
TRACKING
TRIM
I
R1
I
R2
I
Q
=
2I
R2
V+
IR
VIN
R
–
+
Figure 3. Buffer Amplifier Schematic
Philips Semiconductors RF Communications Products
Product specification
NE/SA572
Programmable analog compandor
October 7, 1987
6
Buffer Amplifier
In audio systems, it is desirable to have fast
attack time and slow recovery time for a tone
burst input. The fast attack time reduces
transient channel overload but also causes
low-frequency ripple distortion. The
low-frequency ripple distortion can be
improved with the slow recovery time. If
different attack times are implemented in
corresponding frequency spectrums in a split
band audio system, high quality performance
can be achieved. The buffer amplifier is
designed to make this feature available with
minimum external components. Referring to
Figure 3, the rectifier output current is
mirrored into the input and output of the
unipolar buffer amplifier A
3
through Q
8
, Q
9
and Q
10
. Diodes D
11
and D
12
improve
tracking accuracy and provide
common-mode bias for A
3
. For a
positive-going input signal, the buffer
amplifier acts like a voltage-follower.
Therefore, the output impedance of A
3
makes
the contribution of capacitor CR to attack time
insignificant. Neglecting diode impedance,
the gain Ga(t) for
G can be expressed as
follows:
Ga
(
t
)
(
Ga
INT
Ga
FNL
e
t
A
Ga
FNL
Ga
INT
=Initial Gain
Ga
FNL
=Final Gain
τ
A
=R
A
CA=10k
CA
where
τ
A
is the attack time constant and R
A
is a 10k internal resistor. Diode D
15
opens
the feedback loop of A
3
for a negative-going
signal if the value of capacitor CR is larger
than capacitor CA. The recovery time
depends only on CR
R
R
. If the diode
impedance is assumed negligible, the
dynamic gain G
R
(t) for
G is expressed as
follows.
G
R
(
t
)
(
G
RINT
G
RFNL
e
t
R
G
RFNL
G
R
(t)=(G
R INT
–G
R FNL
) e +G
R FNL
τ
R=R
R
CR=10k
CR
where
τ
R is the recovery time constant and
R
R
is a 10k internal resistor. The gain control
current is mirrored to the gain cell through
Q
14
. The low level gain errors due to input
bias current of A
2
and A
3
can be trimmed
through the tracking trim pin into A
3
with a
current source of
±
3
μ
A.
Basic Expandor
Figure 4 shows an application of the circuit as
a simple expandor. The gain expression of
the system is given by
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SA572N | 功能描述:音頻放大器 Dual Channel Hi Perf RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| SA572NG | 功能描述:音頻放大器 Dual Channel Hi Perf Compandor Ind. Temp RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| SA575 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Low voltage compandor |
| SA5751D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Cell-Phone Circuit |
| SA5752 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Audio processor - companding, VOX and amplifier section |
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