參數(shù)資料
型號: LA3220
元件分類: 音頻/視頻放大
英文描述: 2 CHANNEL, AUDIO PREAMPLIFIER, DIP14
封裝: DIP-14
文件頁數(shù): 6/8頁
文件大?。?/td> 143K
代理商: LA3220
LA3220
No.912-6/9
2. Closed loop gain VG (f = 1kHz)
Closed loop voltage gain is gotten at (f = 1kHz) VG
≈ 20log Z1/Z3
If Z1 = 7.2k
Ω
Z3 = 56
Ω
VG = 20log 7.2
× 103/56 becomes = 42dB.
Therefore, equalizer response is determined by these constants.
So, playback amp gain is :
a. 20log R1/R3 in low frequency regions
b. 20log Z2/Z3 in high frequency regions
Recording amp gain is
VG = 20log R1/R3
3. External constants
External constants are related to the operation starting time of the
amp.
The operation starting time is designed to be within 0.2s, but in this
case it is necessary that the differential TR1 and TR2 is the same in
time constant. The condition is :
C1 (R1//R2) = R5
× C3
Example : If C1 = 220
μF, R1//R2 = 5kΩ, R5 = 51kΩ
then C3 is 22
μF
C1 is a decoupling capacitor, and its capacity changes the ripple rejection rate. (If capacity is large, ripple rejection
rate is large.) It is also related to the amp operation starting time, and when R5, C3 time constant is large, C1 must also
be made large. The recommended value is 220
μF.
C2 is an input capacitor, and more than 4.7μF is recommended.
C3 is an NF capacitor, and determines the low region cut-off frequency. If C3 is increased, operation starting time
lengthens. 10
μF is recommended. The recommended constants therefore are :
R5 (RF)
C1 (CD)
C2 (IN)
C3 (NF)
51k to 100k
Ω
220
μF
4.7
μF
22
μF
200k
Ω
330
μF
10
μF
10
μF
We do not recommended more than 200k
Ω for R5 which lengthens amp operation starting time.
4. Notes on Use
1) Oscillation
When the amp closed loop gain is lowered, oscillation will occur,
so when using it with under 40dB gain, connect 10pF between pin
3 and pin 2, and 0.033
μF (mylar) + 10Ω to the load end. When
closed loop gain is below VG = 30dB, it should not be used.
2) Radio Interference Prevention
Connect about 1000pF between input pin (pin 5) and the ground.
3) Maximu Rating
VCC max is VCC = 14V, and it should not go over this. The recommended power supply voltage is 5V to 13V.
4) Load Impedance
The total load impedance as seen from the output terminal should not be less than 680
Ω.
5) A shrt between pins will cause breakdown or deterioration.
6) A load short will cause breakdown or deterioration.
C2
0.033
μF
z2
z3
z1
R2
4.7k
Ω
R3
56
Ω
C1
22
μF
R1
2
4
51k
Ω
RL
10k
Ω
10
μF
C2
22k
Ω
D1
R1
C1
D2
R2
R4
R5
TR2
TR1
C3
C4
R3
VCC
56
Ω
47k
Ω
10
Ω
RL
51
Ω
0.033
μF
0.033
μF
10
μF
10pF
3
2
5
4
10
μF
20
μF
1000pF
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