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Non-Inverting Compensation
For the non-inverting amp the same theory applies for estab-
lishing the needed compensation. When setting the inverting
configuration for a gain of 1, F has a value of 2. For the non-
inverting configuration both F and the actual gain are the
same, making the non-inverting configuration more difficult to
compensate. Using the same circuit as shown in
Figure 4
, but
setting up the circuit for non-inverting operation (gain of +2)
results in similar performance as the inverting configuration
with the inputs set to half the amplitude to compensate for the
additional gain.
Figure 11
below shows the results.
20216382
FIGURE 11. R
C
= 240
and C = 2.2 nF, Gain = +2
20216383
FIGURE 12. LMV796 Response Gain = +2
The response shown in
Figure 11
is close to the response
shown in
Figure 9
. The part is actually slightly faster in the
non-inverting configuration. Decreasing the value of R
to
around 200
can decrease the negative overshoot but will
have slightly longer rise and fall times. The other option is to
add a small resistor in series with the input signal.
Figure 12
shows the performance of the LMV796 with no compensation.
Again the decompensated parts are almost 2.5 times faster
than the fully compensated op amp.
The most difficult op amp configuration to stabilize is the gain
of +1. With proper compensation the LMV793/LMV794 can
be used in this configuration and still maintain higher speeds
than the fully compensated parts.
Figure 13
shows the gain =
1, or the buffer configuration, for these parts.
20216384
FIGURE 13. LMV793 with Lead-Lag Compensation for
Non-Inverting Configuration
Figure 13
is the result of using
Equation 5
and additional ex-
perimentation in the lab. R
is not part of
Equation 5
, but it is
necessary to introduce another pole at the input stage for
good performance at gain = +1.
Equation 5
is shown below
with R
IN
=
∞
.
Using 2 k
for R
and solving for R
gives R
C
= 2000/6.9 =
290
. The closest standard value for R
C
is 300
. After some
fine tuning in the lab R
= 330
and R
= 1.5 k
were
choosen as the optimum values. R
together with the input
capacitance at the non-inverting pin inserts another pole into
the compensation for the LMV793/LMV794. Adding this pole
and slightly reducing the compensation for 1/F (using a slight-
ly higher resistor value for R
) gives the optimum response
for a gain of +1.
Figure 14
is the response of the circuit shown
in
Figure 13
.
Figure 15
shows the response of the LMV796 in
the buffer configuration with no compensation and R
P
= R
F
=
0.
20216388
FIGURE 14. R
C
= 330
and C = 10 nF, Gain = +1
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMV793MAX/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV793MF | 制造商:Texas Instruments 功能描述:OP AMP, DECOM, 1.8V, 88MHZ, POWERWISE 制造商:Texas Instruments 功能描述:OP AMP, DECOM, 1.8V, 88MHZ, POWERWISE; Op Amp Type:Low Noise; No. of Amplifiers:1; Slew Rate:40V/s; Supply Voltage Range:1.8V to 5.5V; Amplifier Case Style:SOT-23; No. of Pins:5; Bandwidth:88MHz; Operating Temperature Min:-40C; ;RoHS Compliant: Yes |
| LMV793MF/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV793MFX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:88 MHz, Low Noise, 1.8V CMOS Input, Decompensated Operational Amplifiers |
| LMV793MFX/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
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