參數(shù)資料
型號(hào)： OPA694IDR
英文描述： Wideband, Low-Power, Current Feedback Operational Amplifier
中文描述： 寬帶，低功耗，電流反饋運(yùn)算放大器
文件頁(yè)數(shù)： 14/24頁(yè)
文件大?。?/td> 382K
代理商： OPA694IDR
"#$
SBOS319C SEPTEMBER 2004 REVISED NOVEMBER 2004
www.ti.com
14
This is written in a loop-gain analysis format, where the
errors arising from a noninfinite open-loop gain are shown
in the denominator. If Z
(S)
were 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:
Z
(S)
R
I
NG
R
F
Loop Gain
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 reduces to 1 (and
the curves intersect). This point of equality is where the
amplifier closed-loop frequency response given by
Equation (1) starts to roll off, and is exactly analogous to
the frequency at which the noise gain equals the open-loop
voltage gain for a voltage-feedback op amp. The
difference here is that the total impedance in the
denominator of Equation (2) may be controlled somewhat
separately from the desired signal gain (or NG).
The OPA694 is internally compensated to give a
maximally flat frequency response for R
F
= 402
at
NG = 2 on
±
5V supplies. Evaluating the denominator of
Equation (2) (which is the feedback transimpedance)
gives an optimal target of 462
. As the signal gain
changes, the contribution of the NG
×
R
I
term in the
feedback transimpedance will change, but the total can be
held constant by adjusting R
F
. Equation (3) gives an
approximate equation for optimum R
F
over signal gain:
R
F
462
NG
R
I
As the desired signal gain increases, this equation will
eventually predict a negative R
F
. A somewhat subjective
limit to this adjustment can also be set by holding R
G
to a
minimum value of 20
. Lower values will load both the
buffer stage at the input and the output stage, if R
F
gets too
low, actually decreasing the bandwidth. Figure 9 shows
the recommended R
F
versus NG for
±
5V operation. The
values for R
F
versus gain shown here are approximately
equal to the values used to generate the Typical
Characteristics. They differ in that the optimized values
used in the Typical Characteristics are also correcting for
board parasitics not considered in the simplified analysis
leading to Equation (2). The values shown in Figure 9 give
a good starting point for design where bandwidth
optimization is desired.
450
400
350
300
250
200
150
Noise Gain
0
20
10
15
5
F
)
Figure 9. Feedback Resistor vs Noise Gain
The total impedance going into the inverting input may be
used to adjust the closed-loop signal bandwidth. Inserting
a series resistor between the inverting input and the
summing junction will increase the feedback impedance
(denominator of Equation (1)), decreasing the bandwidth.
This approach to bandwidth control is used for the
inverting summing circuit on the front page. The internal
buffer output impedance for the OPA694 is slightly
influenced by the source impedance looking out of the
noninverting input terminal. High source resistors will have
the effect of increasing R
I
, decreasing the bandwidth.
OUTPUT CURRENT AND VOLTAGE
The OPA694 provides output voltage and current
capabilities that are not usually found in wideband
amplifiers. Under no-load conditions at 25
°
C, the output
voltage typically swings closer than 1.2V to either supply
rail; the +25
°
C swing limit is within 1.2V of either rail. Into
a 15
load (the minimum tested load), it is tested to deliver
more than
±
60mA.
The specifications described above, though familiar in the
industry, consider voltage and current limits separately. In
many applications, it is the voltage
×
current, or VI
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 OPA694 output
drive capabilities, noting that the graph is bounded by a
Safe Operating Area
of 1W maximum internal power
(2)
(3)
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
OPA694IDRG4 功能描述:高速運(yùn)算放大器 WideBand Low-Power Curr Feedback Amp 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
OPA695 制造商:BB 制造商全稱:BB 功能描述:Wideband, Low-Power, Current Feedback Operational Amplifier
OPA695ID 功能描述:高速運(yùn)算放大器 Ultra-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
OPA695ID 制造商:Texas Instruments 功能描述:IC SM OP-AMP WIDEBAND CFB
OPA695IDBVR 功能描述:高速運(yùn)算放大器 Ultra-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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