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| 型號(hào)： | OPA2690IDBV |
| 英文描述： | Dual, Wideband, Voltage-Feedback OPERATIONAL AMPLIFIER with Disable |
| 中文描述： | 雙路，寬帶，電壓反饋運(yùn)算放大器具有禁用 |
| 文件頁數(shù)： | 20/30頁 |
| 文件大小： | 494K |
| 代理商： | OPA2690IDBV |
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SBOS238D JUNE 2002 REVISED DECEMBER 2004
www.ti.com
20
feedback resistor. This has the interesting advantage that
the noise gain becomes equal to 2 for a 50
source
impedance—the same as the noninverting circuits
considered in the previous section. The amplifier output,
however, will now see the 100
feedback resistor in
parallel with the external load. In general, the feedback
resistor should be limited to the 200
to 1.5k
range. In
this case, it is preferable to increase both the R
F
and R
G
values (see Figure 8), and then achieve the input matching
impedance with a third resistor (R
M
) to ground. The total
input impedance becomes the parallel combination of R
G
and R
M
.
1/2
OPA2690
50
R
F
402
R
G
200
R
B
146
R
M
67
Source
+5V
5V
R
O
50
0.1
μ
F
6.8
μ
F
+
0.1
μ
F
0.1
μ
F
6.8
μ
F
+
50
Load
V
O
V
I
=
2
V
O
V
I
Figure 12. Gain of 2 Example Circuit
The second major consideration, touched on in the
previous paragraph, is that the signal source impedance
becomes part of the noise gain equation and influences
the bandwidth. For the example in Figure 12, the R
M
value
combines in parallel with the external 50
source
impedance, yielding an effective driving impedance of
50
67
= 28.6
. This impedance is added in series
with R
G
for calculating the noise gain (NG). The resultant
NG is 2.8 for Figure 12, as opposed to only 2 if R
M
could
be eliminated as discussed above. The bandwidth will
therefore be slightly lower for the gain of 2 circuit of
Figure 12 than for the gain of +2 circuit of Figure 1.
The third important consideration in inverting amplifier
design is setting the bias current cancellation resistor on
the noninverting input (R
B
). If this resistor is set equal to the
total DC resistance looking out of the inverting node, the
output DC error, due to the input bias currents, will be
reduced to (Input Offset Current)
×
R
F
. If the 50
source
impedance is DC-coupled in Figure 10, the total
resistance to ground on the inverting input will be 228
.
Combining this in parallel with the feedback resistor gives
the R
B
= 146
used in this example. To reduce the
additional high-frequency noise introduced by this resistor,
it is sometimes bypassed with a capacitor. As long as
R
B
< 350
, the capacitor is not required because the total
noise contribution of all other terms will be less than that
of the op amp input noise voltage. As a minimum, the
OPA2690 requires an R
B
value of 50
to damp out
parasitic-induced peaking—a direct short to ground on the
noninverting input runs the risk of a very high-frequency
instability in the input stage.
OUTPUT CURRENT AND VOLTAGE
The OPA2690 provides exceptional output voltage and
current capabilities in a low-cost monolithic op amp. Under
no-load conditions at +25
°
C, the output voltage typically
swings closer than 1V to either supply rail; the specified
swing limit is within 1.2V of either rail. Into a 15
load (the
minimum tested load), it will deliver more than
±
160mA.
The specifications described previously, though familiar in
the industry, consider voltage and current limits separately.
In many applications, it is the voltage
×
current, or V-I
product, which is more relevant to circuit operation. Refer
to the
Output Voltage and Current Limitations
plot in the
Typical Characteristics. The X- and Y-axes of this graph
show the zero-voltage output current limit and the
zero-current output voltage limit, respectively. The four
quadrants give a more detailed view of the OPA2690
output drive capabilities, noting that the graph is bounded
by a
Safe Operating Area
of 1W maximum internal power
dissipation for each channel separately. Superimposing
resistor load lines onto the plot shows that the OPA2690
can drive
±
2.5V into 25
or
±
3.5V into 50
without
exceeding the output capabilities or the 1W dissipation
limit. A 100
load line (the standard test circuit load)
shows the full
±
3.9V output swing capability (see the
Electrical Characteristics).
The minimum specified output voltage and current
specifications over temperature are set by worst-case
simulations at the cold temperature extreme. Only at cold
startup will the output current and voltage decrease to the
numbers shown in the Electrical Characteristic tables. As
the output transistors deliver power, their junction
temperatures increase, decreasing their V
BE
s (increasing
the available output voltage swing) and increasing their
current gains (increasing the available output current). In
steady-state operation, the available output voltage and
current is always greater than that shown in the
over-temperature specifications because the output stage
junction temperatures will be higher than the minimum
specified operating ambient.
To protect the output stage from accidental shorts to
ground and the power supplies, output short-circuit
protection is included in the OPA2690. The circuit acts to
limit the maximum source or sink current to approximately
250mA.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA2690IDG4 | 功能描述:高速運(yùn)算放大器 Dual Wideband Voltage Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA2690IDR | 功能描述:高速運(yùn)算放大器 Dual Wide Band RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA2690IDRG4 | 功能描述:高速運(yùn)算放大器 Dual Wideband Voltage Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA2691I-14D | 功能描述:高速運(yùn)算放大器 Dual Wideband Current Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| OPA2691I-14DG4 | 功能描述:高速運(yùn)算放大器 Dual Wideband Current Feedback RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 電壓增益 dB:116 dB 輸入補(bǔ)償電壓:0.5 mV 轉(zhuǎn)換速度:55 V/us 工作電源電壓:36 V 電源電流:7.5 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
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