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參數(shù)資料
| 型號(hào)： | OPA620 |
| 英文描述： | Wideband Precision OPERATIONAL AMPLIFIER |
| 中文描述： | 寬帶高精度運(yùn)算放大器 |
| 文件頁數(shù)： | 11/15頁 |
| 文件大?。?/td> | 309K |
| 代理商： | OPA620 |
11
OPA620
Many demanding high-speed applications such as ADC/
DAC buffers require op amps with low wideband output
impedance. For example, low output impedance is essential
when driving the signal-dependent capacitances at the inputs
of flash A/D converters. As shown in Figure 3, the OPA620
maintains very low closed-loop output impedance over
frequency. Closed-loop output impedance increases with
frequency since loop gain is decreasing with frequency.
100
1k
10k
100k
1M
10M
100M
Frequency (Hz)
10
1
0.1
0.01
S
G = +10V/V
G = +1V/V
G = +2V/V
FIGURE 3. Small-Signal Output Impedance vs Frequency.
THERMAL CONSIDERATIONS
The OPA620 does not require a heat sink for operation in
most environments. The use of a heat sink, however, will
reduce the internal thermal rise and will result in cooler,
more reliable operation. At extreme temperatures and under
full load conditions a heat sink is necessary. See “Maximum
Power Dissipation” curve, Figure 4.
FIGURE 4. Maximum Power Dissipation.
The internal power dissipation is given by the equation P
=
P
DQ
+ P
, where P
is the quiescent power dissipation and
P
is the power dissipation in the output stage due to the
load. (For
±
V
=
±
5V, P
= 10V
x
23mA = 230mW, max).
For the case where the amplifier is driving a grounded load
(R
) with a DC voltage (
±
V
) the maximum value of P
occurs at
±
V
=
±
V
/2, and is equal to P
, max =
(
±
V
)
2
/4R
. Note that it is the voltage across the output
transistor, and not the load, that determines the power
dissipated in the output stage.
When the output is shorted to ground, P
DL
= 5V
x
150mA =
750mW. Thus, P
= 230mW + 750mW
≈
1W. Note that the
short-circuit condition represents the maximum amount of
internal power dissipation that can be generated. Thus, the
“Maximum Power Dissipation” curve starts at 1W and is
derated based on a 175
°
C maximum junction temperature
and the junction-to-ambient thermal resistance,
θ
, of each
package. The variation of short-circuit current with tempera-
ture is shown in Figure 5.
FIGURE 6. Driving Capacitive Loads.
OPA620
C
L
R
L
R
S
(R typically 5 to 25 )
CAPACITIVE LOADS
The OPA620’s output stage has been optimized to drive
resistive loads as low as 50
. Capacitive loads, however,
will decrease the amplifier’s phase margin which may cause
high frequency peaking or oscillations. Capacitive loads
greater than 20pF should be buffered by connecting a small
resistance, usually 5
to 25
, in series with the output as
shown in Figure 6. This is particularly important when
driving high capacitance loads such as flash A/D converters.
In general, capacitive loads should be minimized for
optimum high frequency performance. Coax lines can be
driven if the cable is properly terminated. The capacitance of
coax cable (29pF/foot for RG-58) will not load the amplifier
when the coaxial cable or transmission line is terminated in
its characteristic impedance.
FIGURE 5. Short-Circuit Current vs Temperature.
250
200
150
100
50
–75
–50
–25
0
+25
+50
+75
+100
+125
S
Ambient Temperature (°C)
+I
SC
– I
SC
Cerdip
Package
1.2
1.0
0.8
0.6
0.4
0.2
0
0
+25
+50
+75
+100
+125
+150
Ambient Temperature (°C)
I
Plastic DIP, SO-8
Packages
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| OPA620KP | Wideband Precision OPERATIONAL AMPLIFIER |
| OPA620KU | Wideband Precision OPERATIONAL AMPLIFIER |
| OPA621 | Wideband Precision OPERATIONAL AMPLIFIER |
| OPA621KP | |
| OPA621KU | |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA620KP | 制造商:Rochester Electronics LLC 功能描述: 制造商:BB 功能描述: 制造商:Texas Instruments 功能描述: |
| OPA620KU | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| OPA620SG | 制造商:BB 制造商全稱:BB 功能描述:Wideband Precision OPERATIONAL AMPLIFIER |
| OPA621 | 制造商:BB 制造商全稱:BB 功能描述:Wideband Precision OPERATIONAL AMPLIFIER |
| OPA621KP | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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