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參數(shù)資料
| 型號(hào)： | OPA683ID |
| 元件分類： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | OP-AMP|SINGLE|BIPOLAR|SOP|8PIN|PLASTIC |
| 中文描述： | 運(yùn)放|單|雙極|?？苵 8引腳|塑料 |
| 文件頁(yè)數(shù)： | 16/24頁(yè) |
| 文件大?。?/td> | 400K |
| 代理商： | OPA683ID |
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OPA683
SBOS221B
16
www.ti.com
A current-feedback op amp senses an error current in the
inverting node (as opposed to a differential input error volt-
age for a voltage feedback op amp) and passes this on to the
output through an internal frequency dependent transimped-
ance gain. The Typical Characteristics show this open-loop
transimpedance response. This is analogous to the open-
loop voltage gain curve for a voltage feedback op amp.
Developing the transfer function for the circuit of Figure 10
gives Equation 1:
(1)
V
V
R
R
R
R
R
R
Z
NG
+
R
R NG
Z
NG
R
R
O
I
F
G
F
I
F
G
S
F
S
F
G
=
+
+
+
+
=
+
=
+
α
α
1
1
1
1
1
( )
( )
This is written in a loop-gain analysis format where the errors
arising from a non-infinite open-loop gain are shown in the
denominator. If Z(s) was infinite over all frequencies, the
denominator of Equation 1 would reduce to 1 and the ideal
desired signal gain shown in the numerator would be achieved.
The fraction in the denominator of Equation 1 determines the
frequency response. Equation 2 shows this as the loop-gain
equation.
(2)
Z
+
R
R NG
Loop Gain
S
F
( )
=
If 20
log(R
F
+ NG
R
I
) were drawn on top of the open-loop
transimpedance plot, the difference between the two would
be the loop gain at a given frequency. Eventually, Z(s) rolls
off to equal the denominator of Equation 2 at which point the
loop gain has reduced to 1 (and the curves have intersected).
This point of equality is where the amplifier
’
s closed-loop
frequency response given by Equation 1 will start to roll off,
and is exactly analogous to the frequency at which the noise
gain equals the open-loop voltage gain for a voltage feed-
back op amp. The difference here is that the total impedance
in the denominator of Equation 2 may be controlled some-
what separately from the desired signal gain (or NG).
The OPA683 is internally compensated to give a maximally
flat frequency response for R
F
= 1.2k
at NG = 2 on
±
5V
supplies. That optimum value goes to 1.4k
on a single +5V
supply. Normally, with a current feedback amplifier, it is
possible to adjust the feedback resistor to hold this band-
width up as the gain is increased. The CFB
plus
architecture
has reduced the contribution of the inverting input impedance
to provide exceptional bandwidth to higher gains without
adjusting the feedback resistor value. The Typical Character-
istics show the small-signal bandwidth over gain with a fixed
feedback resistor.
At very high gains, 2nd-order effects in the buffer output
impedance cause the overall response to peak up. If desired,
it is possible to retain a flatter frequency response at higher
gains by adjusting the feedback resistor to higher values as
the gain is increased. Figure 11 shows the empirically deter-
mined feedback resistor and resulting
–
3dB bandwidth from
gains of +2 to +100 to hold a < 0.5dB peaked response.
Here, since a slight peaking was allowed, a lower nominal R
F
is suggested at a gain of +2 giving > 250MHz bandwidth.
This exceeds that shown in the Electrical Characteristics due
to the slightly lower feedback resistor allowing a modest
peaking in the response. Figure 12 shows the measured
frequency response curves with the adjusted feedback resis-
tor value. While the bandwidth for this low-power part does
reduce at higher gains, going over a 50:1 gain range gives
only a factor of 10 bandwidth reduction. The 25MHz band-
width at a gain of 100V/V is equivalent to a 2.5GHz gain
bandwidth product voltage feedback amplifier capability. Even
better bandwidth retention to higher gains can be delivered
by the slightly higher quiescent power OPA684.
3900
3400
2900
2400
1900
1400
900
Voltage Gain (V/V)
2
20
10
R
F
5
50
100
F
)
325
275
225
175
125
75
25
B
–
3dB Bandwidth
V
O
= 0.5Vp-p
3
0
–
3
–
6
–
9
–
12
Frequency (MHz)
1
200
10
100
N
G = 5
G = 100
G = 2
G = 10
G = 50
G = 20
FIGURE 11. Bandwidth and R
F
Optimized vs Gain.
FIGURE 12. Small-Signal Frequency Response with Opti-
mized R
F
.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OPA683IDBVR | 功能描述:高速運(yùn)算放大器 Very Lo-Pwr 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 |
| OPA683IDBVRG4 | 功能描述:高速運(yùn)算放大器 Very Lo-Pwr 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 |
| OPA683IDBVT | 功能描述:高速運(yùn)算放大器 Very Lo-Pwr 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 |
| OPA683IDBVTG4 | 功能描述:高速運(yùn)算放大器 Very Lo-Pwr 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 |
| OPA683IDG4 | 功能描述:高速運(yùn)算放大器 Very Lo-Pwr 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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